Methods and compositions for use in oil and/or gas wells

ABSTRACT

Methods and compositions comprising an emulsion or a microemulsion for use in various aspects of the life cycle of an oil and/or gas well are provided. In some embodiments, the emulsion or the microemulsion comprises water, a solvent, and a surfactant, and optionally, one or more additives.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/946,176 filed Feb. 28, 2014, entitled“Methods and Compositions for Use in Oil and/or Gas Wells”, incorporatedherein by reference in its entirety for all purposes. This applicationis also a continuation-in-part of U.S. patent application Ser. No.13/829,495 filed Mar. 14, 2013, entitled “Methods and Compositions forStimulating the Production of Hydrocarbons from SubterraneanFormations”; a continuation-in-part of U.S. patent application Ser. No.13/829,434 filed Mar. 14, 2013 entitled “Methods and Compositions forStimulating the Production of Hydrocarbons from SubterraneanFormations”; a continuation-in-part of U.S. patent application Ser. No.13/918,155 filed Jun. 14, 2013 entitled “Methods and Compositions forStimulating the Production of Hydrocarbons from SubterraneanFormations”; and a continuation-in-part of U.S. patent application Ser.No. 13/918,166 filed Jun. 14, 2013 entitled “Methods and Compositionsfor Stimulating the Production of Hydrocarbons from SubterraneanFormations,” each of which is incorporated herein by reference in itsentirety for all purposes.

FIELD OF INVENTION

Methods and compositions comprising an emulsion or a microemulsion foruse in various aspects of a life cycle of an oil and/or gas well areprovided.

BACKGROUND OF INVENTION

For many years, petroleum has been recovered from subterraneanreservoirs through the use of drilled wells and production equipment.Oil and natural gas are found in, and produced from, porous andpermeable subterranean formations, or reservoirs. The porosity andpermeability of the formation determine its ability to storehydrocarbons, and the facility with which the hydrocarbons can beextracted from the formation. Generally, the life cycle of an oil and/orgas well includes drilling to form a wellbore, casing, cementing,stimulation, and enhanced or improved oil recovery.

Various aspects of the life cycle of an oil and/or gas well are designedto facilitate the extraction of oil and/or gas from the reservoir viathe wellbore. A wide variety of fluids is utilized during the life cycleof an oil and/or gas well and are well known. In order to improveextraction of oil and/or gas, additives have been incorporated intovarious fluids utilized during the life cycle of an oil and/or gas well.The incorporation of additives into fluids utilized during the lifecycle of an oil and/or gas well can increase crude oil or formation gas,for example, by reducing capillary pressure and/or minimizing capillaryend effects. For example, drilling fluids are utilized to carry cuttingsand other particulates from beneath the drill bit to the surface and canfunction to reduce friction between the drill bit and the sides of thewellbore while maintaining the stability of uncased sections of theborehole. In addition, the drilling fluid and the subsequent cementingand perforating fluids can be formulated to prevent imbibition and/orunwanted influxes of some formation fluids. As another example,fracturing and acidizing are a commonly used techniques to stimulate theproduction of oil and/or gas from reservoirs, wherein a stimulationfluid is injected into the wellbore and the formation (reservoir). In atypical matrix acidizing or fracturing treatment, from 1 barrel per footto several million gallons of stimulation fluid are pumped into areservoir (e.g., via the wellbore). The stimulation fluid can compriseadditives to aid in the stimulation process, for example, proppants,scale inhibitors, friction reducers, biocides, gases such as carbondioxide and nitrogen, acids, slow release acids, corrosion inhibitors,buffers, viscosifiers, clay swelling inhibitors, oxygen scavengers, andsurfactants. Later in the life of the well additional fluids and gasesmay be injected into the well to remediate damage, maintain pressure orcontact and recover further oil.

When selecting or using a fluid to be utilized during the life cycle ofan oil and/or gas well, it is important for the fluid to comprise theright combination of additives and components to achieve the necessarycharacteristics of the specific end-use application. A primary goalamongst all aspects of the life cycle of a well is to optimize recoveryof oil and/or gas from the reservoir. However, in part because thefluids utilized during the life cycle of an oil and/or gas well areoften utilized to perform a number of tasks simultaneously, achievingnecessary to optimal characteristics is not always easy.

Accordingly, it would be desirable if a wide variety of additives wereavailable which could be selected to achieve the necessarycharacteristics and/or could be easily adapted. Furthermore, it isdesirable that the additives provide multiple benefits and are usefulacross multiple portions of the life cycle of the well. For example, achallenge often encountered is fluid recovery following injection offracturing fluids or other fluids into the wellbore. Often, largequantities of injected fluids are trapped in the formation, for example,in the area surrounding the fracture and within the fracture itself. Itis theorized that the trapping of the fluid is due to interfacialtension between water and reservoir rock and/or capillary end effects inand around the vicinity of the face of the fractured rock. The presenceof trapped fluids generally has a negative effect on the productivity ofthe well. While several approaches have been used to overcome thisproblem, for example, incorporation of co-solvents and/or surfactants(i.e., low surface tension fluids), there is still the need for improvedadditives, as well as a greater understanding as to how to select theadditives to maximize the productivity of the well. The use ofmicroemulsions has also been employed, however, selection of anappropriate microemulsion for a particular application remainschallenging, as well as there is a continued need for emulsions withenhanced abilities.

Accordingly, although a number of additives are known in the art, thereis a continued need for more effective additives for increasingproduction of oil and/or gas.

SUMMARY OF INVENTION

Methods and compositions comprising an emulsion or a microemulsion foruse in various aspects of the life-cycle of an oil and/or gas well areprovided.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a fluid comprising anemulsion or microemulsion into the wellbore, wherein the emulsion ormicroemulsion comprises an aqueous phase; a surfactant; and a solvent,wherein the solvent comprises an amine of the formula NR¹R²R³, whereineach of R¹, R², and R³ are the same or different and are alkyl, provideat least one of R¹, R², and R³ is methyl or ethyl, or optionally,wherein any two of R¹, R², and R³ are joined together to form a ring;and wherein the pH of the fluid is about neutral or greater.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a fluid comprising anemulsion or microemulsion into the wellbore, wherein the emulsion ormicroemulsion comprises an aqueous phase; a surfactant; and a solvent,wherein the solvent comprises an amide of the formula (C═OR⁴)R⁵R⁶,wherein each of R⁴, R⁵, and R⁶ are the same or different and arehydrogen or alkyl, or optionally, R⁵ and R⁶ are joined together to forma ring.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a fluid comprising anemulsion or microemulsion into the wellbore, wherein the emulsion ormicroemulsion comprises water; an alcohol; a solvent comprising aterpene; and a surfactant, wherein the surfactant has a structure as inFormula I:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; R¹² is hydrogen or alkyl;n is 1-100; and each m is independently 1 or 2.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a fluid comprising anemulsion or microemulsion into the wellbore, wherein the emulsion ormicroemulsion comprise water; an alcohol; a solvent comprising aterpene; and a surfactant, wherein the surfactant has a structure as inFormula II:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; Y⁻ is an anionic group;X⁺ is a cationic group; n is 1-100; and each m is independently 1 or 2.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a fluid comprising anemulsion or microemulsion into the wellbore, wherein the emulsion ormicroemulsion comprises water; an alcohol; a solvent comprising aterpene; and a surfactant, wherein the surfactant has a structure as inFormula III:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; Z⁺ is a cationic group; nis 1-100; and each m is independently 1 or 2.

In some embodiments, a method of treating an oil and/or gas well havinga wellbore is provided comprising injecting a solution into thewellbore, wherein the solution comprising a fluid selected from thegroup consisting of a mud displacement fluid, a cementing fluid, aperforating fluid, a kill fluid, and EOR/IOR fluid, a stored fluid, or astimulation fluid utilized in offshore wells or during fracture packing,and an emulsion or microemulsion, wherein the emulsion or themicroemulsion comprises between about 1 wt % and 95 wt % water; betweenabout 1 wt % and 99 wt % solvent; between about 0 wt % and about 50 wt %alcohol; between about 1 wt % and 90 wt % surfactant; between about 0 wt% and about 70 wt % freezing point depression agent; and between about 0wt % and about 70 wt % other additives.

In some embodiments, a composition for use in an oil and/or gas wellhaving a wellbore is provided comprising a fluid and an emulsion ormicroemulsion, wherein the emulsion or the microemulsion compriseswater; an alcohol; a solvent comprising a terpene; and a surfactant inan amount between about 9 wt % and about 11 wt % versus the totalemulsion, wherein the surfactant has a structure as in Formula I:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; R¹² is hydrogen or alkyl;n is 1-100; and each m is independently 1 or 2.

In some embodiments, a composition for use in an oil and/or gas wellhaving a wellbore is provided comprising a fluid and an emulsion ormicroemulsion, wherein the emulsion or the microemulsion compriseswater; an alcohol; a solvent comprising a terpene; and a surfactant inan amount between about 9 wt % and about 11 wt % versus the totalemulsion, wherein the surfactant has a structure as in Formula II:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; Y⁻ is an anionic group;X⁺ is a cationic group; n is 1-100; and each m is independently 1 or 2.

In some embodiments, a composition for use in an oil and/or gas wellhaving a wellbore is provided comprising a fluid and an emulsion ormicroemulsion, wherein the emulsion or the microemulsion compriseswater; an alcohol; a solvent comprising a terpene; and a surfactant inan amount between about 9 wt % and about 11 wt % versus the totalemulsion, wherein the surfactant has a structure as in Formula III:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, provided at least one of R⁷, R⁸, R⁹,R¹⁰, and R¹¹ is —CH═CHAr; Ar is an aryl group; Z⁺ is a cationic group; nis 1-100; and each m is independently 1 or 2.

Other aspects, embodiments, and features of the methods and compositionswill become apparent from the following detailed description whenconsidered in conjunction with the accompanying drawings. All patentapplications and patents incorporated herein by reference areincorporated by reference in their entirety. In case of conflict, thepresent specification, including definitions, will control.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 shows an exemplary plot for determining the phase inversiontemperature of a microemulsion, according to some embodiments.

DETAILED DESCRIPTION

Methods and compositions comprising an emulsion or a microemulsion foruse in various aspects of the life cycle of an oil and/or gas well areprovided. An emulsion or a microemulsion may comprise water, a solvent,a surfactant, a co-surfactant (e.g., an alcohol), and optionally othercomponents (e.g., a clay stabilizer, a freezing point depression agent,an acid, a salt, etc.). In some embodiments, the solvent comprises morethan one type of solvent (e.g., a first type of solvent and a secondtype of solvent). In some embodiments, the methods and compositionsrelate to various aspects of the life cycle of an oil and/or gas well(e.g., drilling, mud displacement, casing, cementing, perforating,stimulation, kill fluids, enhanced oil recovery/improved oil recovery,etc.). In some embodiments, an emulsion or a microemulsion is added to afluid utilized in the life cycle of well thereby increasing hydrocarbon(e.g., liquid or gaseous) production of the well, improving recovery ofthe fluid and/or other fluids, and/or preventing or minimizing damage tothe well caused by exposure to the fluid (e.g., from imbibition).

Additional details regarding the emulsion or microemulsions, as well asthe applications of the emulsions or microemulsions, are describedherein. For example, the emulsions and microemulsions described in theSection A may be utilized in any a wide variety of application in thelife cycle of the well, as described in Section B.

I. Emulsions and Microemulsions

In some embodiments, emulsions or microemulsion are provided. The termsshould be understood to include emulsions or microemulsions that have awater continuous phase, or that have an oil continuous phase, ormicroemulsions that are bicontinuous or multiple continuous phases ofwater and oil.

As used herein, the term emulsion is given its ordinary meaning in theart and refers to dispersions of one immiscible liquid in another, inthe form of droplets, with diameters approximately in the range of100-1,000 nanometers. Emulsions may be thermodynamically unstable and/orrequire high shear forces to induce their formation.

As used herein, the term microemulsion is given its ordinary meaning inthe art and refers to dispersions of one immiscible liquid in another,in the form of droplets, with diameters approximately in the range ofabout between about 1 and about 1000 nm, or between 10 and about 1000nanometers, or between about 10 and about 500 nm, or between about 10and about 300 nm, or between about 10 and about 100 nm. Microemulsionsare clear or transparent because they contain particles smaller than thewavelength of visible light. In addition, microemulsions are homogeneousthermodynamically stable single phases, and form spontaneously, andthus, differ markedly from thermodynamically unstable emulsions, whichgenerally depend upon intense mixing energy for their formation.Microemulsions may be characterized by a variety of advantageousproperties including, by not limited to, (i) clarity, (ii) very smallparticle size, (iii) ultra-low interfacial tensions, (iv) the ability tocombine properties of water and oil in a single homogeneous fluid, (v)shelf life stability, and (vi) ease of preparation.

In some embodiments, the microemulsions described herein are stabilizedmicroemulsions that are formed by the combination of asolvent-surfactant blend with an appropriate oil-based or water-basedcarrier fluid. Generally, the microemulsion forms upon simple mixing ofthe components without the need for high shearing generally required inthe formation of ordinary emulsions. In some embodiments, themicroemulsion is a thermodynamically stable system, and the dropletsremain finely dispersed over time. In some cases, the average dropletsize ranges from about 10 nm to about 300 nm.

It should be understood, that while much of the description hereinfocuses on microemulsions, this is by no means limiting, and emulsionsmay be employed where appropriate.

In some embodiments, the emulsion or microemulsion is a single emulsionor microemulsion. For example, the emulsion or microemulsion comprises asingle layer of a surfactant. In other embodiments, the emulsion ormicroemulsion may be a double or multilamellar emulsion ormicroemulsion. For example, the emulsion or microemulsion comprises twoor more layers of a surfactant. In some embodiments, the emulsion ormicroemulsion comprises a single layer of surfactant surrounding a core(e.g., one or more of water, oil, solvent, and/or other additives) or amultiple layers of surfactant (e.g., two or more concentric layerssurrounding the core). In certain embodiments, the emulsion ormicroemulsion comprises two or more immiscible cores (e.g., one or moreof water, oil, solvent, and/or other additives which have equal or aboutequal affinities for the surfactant).

In some embodiments, a microemulsion comprises water, a solvent, and asurfactant. In some embodiments, the microemulsion further comprisesadditional components, for example, a freezing point depression agent.Details of each of the components of the microemulsions are described indetail herein. In some embodiments, the components of the microemulsionsare selected so as to reduce or eliminate the hazards of themicroemulsion to the environment and/or the subterranean reservoirs.

In some embodiments, the emulsion or microemulsion comprise betweenabout 1 wt % and 95 wt % water, between about 1 wt % and 99 wt %solvent, between about 0 wt % and about 50 wt % alcohol, between about 1wt % and 90 wt % surfactant, and between about 0 wt % and about 70 wt %freezing point depression agent, and between about 0 wt % and about 70wt % other additives, versus the total microemulsion composition. Insome embodiments, the emulsion or microemulsion comprise between about 1wt % and 60 wt % water, between about 1 wt % and 30 wt % solvent,between about 1 wt % and about 50 wt % alcohol, between about 5 wt % and65 wt % surfactant, and between about 0 wt % and about 25 wt % freezingpoint depression agent, and between about 0 wt % and about 30 wt % otheradditives, versus the total microemulsion composition. In someembodiments, for the formulation above, the water is present in anamount between about 10 wt % and about 55 wt %, or between about 15 wt %and about 45 wt %. In some embodiments, for the formulation above thesolvent is present in an amount between about 2 wt % and about 25 wt %,or between about 5 wt % and about 25 wt %. In some embodiments, thesolvent comprises a terpene. In some embodiments, for the formulationsabove, the alcohol is present in an amount between about 5 wt % andabout 40 wt %, or between about 5 wt % and 35 wt %. In some embodiments,the alcohol comprises isopropanol. In some embodiments, for theformulations above, the surfactant is present in an amount between about5 wt % and 60 wt %, or between about 10 wt % and 55 wt %. In someembodiments, for the formulations above, the freezing point depressionagent is present in an amount between about 1 wt % and about 25 wt %, orbetween about 1 wt % and about 20 wt %, or between about 3 wt % andabout 20 wt %. In some embodiments, for the formulations above, theother additives are present in an amount between about 1 wt % and about30 wt %, or between about 1 wt % and about 25 wt %, or between about 1wt % and about 20 wt %. In some embodiments, the other additivescomprise one or more salts and/or one or more acids.

In some embodiments, a microemulsion composition comprises between about5 wt % to about 60 wt % water, from about 2 wt % to about 50 wt %solvent, from about 5 wt % to about 60 wt % of a first type of asolubilizing surfactant, from about 2 wt % to about 50 wt % of alcohol,from about 0.5 to 30 wt % of a freezing point depression agent, fromabout 0.5 wt % to about 30 wt % of a second type of surfactant, fromabout 0 wt % to about 70 wt % of other additives (e.g., acid), and fromabout 0.5 wt % to about 30% of mutual solvent, which is miscibletogether with the water and the solvent. In some embodiments, thesolvent is a substance with a significant hydrophobic character withlinear, branched, cyclic, bicyclic, saturated or unsaturated structure,including but not limited to terpenes, terpineols, terpene alcohols,aldehydes, ketones, esters, amines, and amides. Non-limiting examples ofsuitable mutual solvents include ethyleneglycolmonobutyl ether (EGMBE),dipropylene glycol monomethyl ether, short chain alcohols (e.g.,isopropanol), tetrahydrofuran, dioxane, dimethylformamide, anddimethylsulfoxide. Freezing point depressions agents are described inmore detail herein, and include, but are not limited to, alkali metal orearth alkali metal salts, preferably chlorides, urea, alcohols (e.g.,glycols such as propylene glycol and triethylene glycol). In someembodiments, the solubilizing surfactant is a molecule capable offorming a colloidal solution of the said solvent in predominantlyaqueous media. Generally, surfactants are amphiphilic molecules thatadsorb at interfaces to lower surface energy and can be used to formmicroemulsions in which they stabilize a mixture of polar and non-polarsolvent. Non-limiting examples of suitable surfactants include nonionicsurfactants with linear or branched structure, including, but notlimited to, ethoxylated fatty alcohols, ethoxylated castor oils, andalkyl glucosides with a hydrocarbon chain of at least 8 carbon atoms andmole % of ethoxylation of 5 or more. Additional surfactants aredescribed herein. Non-limiting examples of second types of surfactantsinclude adsorption modifiers, foamers, surface tension loweringenhancers, and emulsion breaking additives. Specific examples of suchsurfactants include cationic surfactants with a medium chain length,linear or branched anionic surfactants, amine oxides, amphotericsurfactants, silicone based surfactants, alkoxylated novolac resins(e.g. alkoxylated phenolic resins), alkoxylated polyimines, alkoxylatedpolyamines, and fluorosurfactants.

In some embodiments, the emulsion or microemulsion is as described inU.S. Pat. No. 7,380,606 and entitled “Composition and Process for WellCleaning,” herein incorporated by reference.

I-A. Solvents

The microemulsion generally comprises a solvent. The solvent, or acombination of solvents, may be present in the microemulsion in anysuitable amount. In some embodiments, the total amount of solventpresent in the microemulsion is between about 1 wt % and about 99 wt %,or between about 2 wt % and about 90 wt %, or between about 1 wt % andabout 60 wt %, or between about 2 wt % and about 60 wt %, or betweenabout 1 and about 50 wt %, or between about 1 and about 30 wt %, orbetween about 5 wt % and about 40 wt %, or between about 5 wt % andabout 30 wt %, or between about 2 wt % and about 25 wt %, or betweenabout 5 wt % and about 25 wt %, or between about 60 wt % and about 95 wt%, or between about 70 wt % or about 95 wt %, or between about 75 wt %and about 90 wt %, or between about 80 wt % and about 95 wt %, versusthe total microemulsion composition.

Those of ordinary skill in the art will appreciate that microemulsionscomprising more than two types of solvents may be utilized in themethods, compositions, and systems described herein. For example, themicroemulsion may comprise more than one or two types of solvent, forexample, three, four, five, six, or more, types of solvents. In someembodiments, the microemulsion comprises a first type of solvent and asecond type of solvent. The first type of solvent to the second type ofsolvent ratio in a microemulsion may be present in any suitable ratio.In some embodiments, the ratio of the first type of solvent to thesecond type of solvent by weight is between about 4:1 and 1:4, orbetween 2:1 and 1:2, or about 1:1.

I-A1. Hydrocarbon Solvents

In some embodiments, the solvent is an unsubstituted cyclic or acyclic,branched or unbranched alkane having 6-12 carbon atoms. In someembodiments, the cyclic or acyclic, branched or unbranched alkane has6-10 carbon atoms. Non-limiting examples of unsubstituted acyclicunbranched alkanes having 6-12 carbon atoms include hexane, heptane,octane, nonane, decane, undecane, and dodecane. Non-limiting examples ofunsubstituted acyclic branched alkanes having 6-12 carbon atoms includeisomers of methylpentane (e.g., 2-methylpentane, 3-methylpentane),isomers of dimethylbutane (e.g., 2,2-dimethylbutane,2,3-dimethylbutane), isomers of methylhexane (e.g., 2-methylhexane,3-methylhexane), isomers of ethylpentane (e.g., 3-ethylpentane), isomersof dimethylpentane (e.g., 2,2,-dimethylpentane, 2,3-dimethylpentane,2,4-dimethylpentane, 3,3-dimethylpentane), isomers of trimethylbutane(e.g., 2,2,3-trimethylbutane), isomers of methylheptane (e.g.,2-methylheptane, 3-methylheptane, 4-methylheptane), isomers ofdimethylhexane (e.g., 2,2-dimethylhexane, 2,3-dimethylhexane,2,4-dimethylhexane, 2,5-dimethylhexane, 3,3-dimethylhexane,3,4-dimethylhexane), isomers of ethylhexane (e.g., 3-ethylhexane),isomers of trimethylpentane (e.g., 2,2,3-trimethylpentane,2,2,4-trimethylpentane, 2,3,3-trimethylpentane, 2,3,4-trimethylpentane),and isomers of ethylmethylpentane (e.g., 3-ethyl-2-methylpentane,3-ethyl-3-methylpentane). Non-limiting examples of unsubstituted cyclicbranched or unbranched alkanes having 6-12 carbon atoms, includecyclohexane, methylcyclopentane, ethylcyclobutane, propylcyclopropane,isopropylcyclopropane, dimethylcyclobutane, cycloheptane,methylcyclohexane, dimethylcyclopentane, ethylcyclopentane,trimethylcyclobutane, cyclooctane, methylcycloheptane,dimethylcyclohexane, ethylcyclohexane, cyclononane, methylcyclooctane,dimethylcycloheptane, ethylcycloheptane, trimethylcyclohexane,ethylmethylcyclohexane, propylcyclohexane, and cyclodecane. In aparticular embodiment, the unsubstituted cyclic or acyclic, branched orunbranched alkane having 6-12 carbon is selected from the groupconsisting of heptane, octane, nonane, decane, 2,2,4-trimethylpentane(isooctane), and propylcyclohexane.

In some embodiments, the solvent is an unsubstituted acyclic branched orunbranched alkene having one or two double bonds and 6-12 carbon atoms.In some embodiments, the solvent is an unsubstituted acyclic branched orunbranched alkene having one or two double bonds and 6-10 carbon atoms.Non-limiting examples of unsubstituted acyclic unbranched alkenes havingone or two double bonds and 6-12 carbon atoms include isomers of hexene(e.g., 1-hexene, 2-hexene), isomers of hexadiene (e.g., 1,3-hexadiene,1,4-hexadiene), isomers of heptene (e.g., 1-heptene, 2-heptene,3-heptene), isomers of heptadiene (e.g., 1,5-heptadiene, 1-6,heptadiene), isomers of octene (e.g., 1-octene, 2-octene, 3-octene),isomers of octadiene (e.g., 1,7-octadiene), isomers of nonene, isomersof nonadiene, isomers of decene, isomers of decadiene, isomers ofundecene, isomers of undecadiene, isomers of dodecene, and isomers ofdodecadiene. In some embodiments, the acyclic unbranched alkene havingone or two double bonds and 6-12 carbon atoms is an alpha-olefin (e.g.,1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene,1-dodecene). Non-limiting examples unsubstituted acyclic branchedalkenes include isomers of methylpentene, isomers of dimethylpentene,isomers of ethylpentene, isomers of methylethylpentene, isomers ofpropylpentene, isomers of methylhexene, isomers of ethylhexene, isomersof dimethylhexene, isomers of methylethylhexene, isomers ofmethylheptene, isomers of ethylheptene, isomers of dimethylhexptene, andisomers of methylethylheptene. In a particular embodiment, theunsubstituted acyclic unbranched alkene having one or two double bondsand 6-12 carbon atoms is selected from the group consisting of 1-octeneand 1,7-octadiene.

In some embodiments, the solvent is a cyclic or acyclic, branched orunbranched alkane having 9-12 carbon atoms and substituted with only an—OH group. Non-limiting examples of cyclic or acyclic, branched orunbranched alkanes having 9-12 carbon atoms and substituted with only an—OH group include isomers of nonanol, isomers of decanol, isomers ofundecanol, and isomers of dodecanol. In a particular embodiment, thecyclic or acyclic, branched or unbranched alkane having 9-12 carbonatoms and substituted with only an —OH group is selected from the groupconsisting of 1-nonanol and 1-decanol.

In some embodiments, the solvent is a branched or unbrancheddialkylether compound having the formula C_(n)H_(2n+1)OC_(m)H_(2m+1)wherein n+m is between 6 and 16. In some cases, n+m is between 6 and 12,or between 6 and 10, or between 6 and 8. Non-limiting examples ofbranched or unbranched dialkylether compounds having the formulaC_(n)H_(2n+1)OC_(m)H_(2m+1) include isomers of C₃H₇OC₃H₇, isomers ofC₄H₉OC₃H₇, isomers of C₅H₁₁OC₃H₇, isomers of C₆H₁₃OC₃H₇, isomers ofC₄H₉OC₄H₉, isomers of C₄H₉OC₅H₁₁, isomers of C₄H₉OC₆H₁₃, isomers ofC₅H₁₁OC₆H₁₃, and isomers of C₆H₁₃OC₆H₁₃. In a particular embodiment, thebranched or unbranched dialklyether is an isomer C₆H₁₃OC₆H₁₃ (e.g.,dihexylether).

In some embodiments, the solvent is an aromatic solvent having a boilingpoint between about 300-400° F. Non-limiting examples of aromaticsolvents having a boiling point between about 300-400° F. includebutylbenzene, hexylbenzene, mesitylene, light aromatic naphtha, andheavy aromatic naphtha.

In some embodiments, the solvent is a bicyclic hydrocarbon solvent withvarying degrees of unsaturation including fused, bridgehead, andspirocyclic compounds. Non-limiting examples of bicyclic solventsinclude isomers of decalin, tetrahydronapthalene, norbornane,norbornene, bicyclo[4.2.0]octane, bicyclo[3.2.1]octane, andspiro[5.5]dodecane.

In some embodiments, the solvent is a bicyclic hydrocarbon solvent withvarying degrees of unsaturation and containing at least one O, N, or Satom including fused, bridgehead, and spirocyclic compounds.Non-limiting examples include isomers of 7 oxabicyclo[2.2.1]heptane,4,7-epoxyisobenzofuran-1,3-dione, and 7oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 2,3-dimethyl ester.

In some embodiments, the solvent is a cyclic or acyclic, branched orunbranched alkane having 8 carbon atoms and substituted with only an —OHgroup. Non-limiting examples of cyclic or acyclic, branched orunbranched alkanes having 8 carbon atoms and substituted with only an—OH group include isomers of octanol (e.g., 1-octanol, 2-octanol,3-octanol, 4-octanol), isomers of methyl heptanol, isomers ofethylhexanol (e.g., 2-ethyl-1-hexanol, 3-ethyl-1-hexanol,4-ethyl-1-hexanol), isomers of dimethylhexanol, isomers ofpropylpentanol, isomers of methylethylpentanol, and isomers oftrimethylpentanol. In a particular embodiment, the cyclic or acyclic,branched or unbranched alkane having 8 carbon atoms and substituted withonly an —OH group is selected from the group consisting of 1-octanol and2-ethyl-1-hexanol.

I-A2. Amine and Amide Solvents

In some embodiments, the amine is of the formula NR¹R²R³, wherein R¹,R², and R³ are the same or different and are hydrogen or cyclic oracyclic, branched or unbranched alkyl (e.g., C₁₋₁₆ alkyl), optionallysubstituted, or optionally, any two of R¹, R² and R³ are joined togetherto form a ring. In some embodiments, each of R¹, R², and R³ are the sameor different and are hydrogen or cyclic or acyclic, branched orunbranched alkyl, or optionally, any two of R¹, R² and R³ are joinedtogether to form a ring, provide at least one of R¹, R², and R³ ismethyl or ethyl. In some cases, R¹ is cyclic or acyclic, branched orunbranched C₁-C₆ alkyl and R² and R³ are the same or different and arehydrogen or cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl), or optionally, R² and R³ may be joined together to form a ring.In some cases, R¹ is methyl or ethyl and R₂ and R₃ are the same ordifferent and are hydrogen or cyclic or acyclic, branched or unbranchedalkyl (e.g., C₈₋₁₆ alkyl), or optionally, R² and R³ may be joinedtogether to form a ring. In some cases, R¹ is methyl and R² and R³ arethe same or different and are hydrogen or cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), or optionally, R² and R³ may bejoined together to form a ring. In some cases, R¹ and R² are the same ordifferent and are hydrogen or cyclic or acyclic, branched or unbranchedC₁-C₆ alkyl and R³ is branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl).In some cases, R¹ and R² are the same or different and are methyl orethyl and R³ is hydrogen or cyclic or acyclic, branched or unbranchedalkyl (e.g., C₈₋₁₆ alkyl). In some cases, R¹ and R² are methyl and R³ ishydrogen or cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl).

In some embodiments, the amine is of the formula NR¹R²R³, wherein R¹,R², and R³ are the same or different and are cyclic or acyclic, branchedor unbranched alkyl (e.g., C₁₋₁₆ alkyl), optionally substituted, oroptionally, any two of R¹, R² and R³ are joined together to form a ring.In some embodiments, each of R¹, R², and R³ are the same or differentand are cyclic or acyclic, branched or unbranched alkyl, or optionally,any two of R¹, R² and R³ are joined together to form a ring, provide atleast one of R¹, R², and R³ is methyl or ethyl. In some cases, R¹ iscyclic or acyclic, branched or unbranched C₁-C₆ alkyl and R² and R³ arethe same or different and are cyclic or acyclic, branched or unbranchedalkyl (e.g., C₈₋₁₆ alkyl), or optionally, R² and R³ may be joinedtogether to form a ring. In some cases, R¹ is methyl or ethyl and R₂ andR₃ are the same or different and are cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), or optionally, R² and R³ may bejoined together to form a ring. In some cases, R¹ is methyl and R² andR³ are the same or different and are cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), or optionally, R² and R³ may bejoined together to form a ring. In some cases, R¹ and R² are the same ordifferent and are cyclic or acyclic, branched or unbranched C₁-C₆ alkyland R³ is branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl). In somecases, R¹ and R² are the same or different and are methyl or ethyl andR³ is cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl). In some cases, R¹ and R² are methyl and R³ is cyclic or acyclic,branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl).

In some embodiments, the amine is of the formula NR¹R²R³, wherein R¹ ismethyl and R² and R³ are the same or different and are hydrogen orcyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl, or optionally R²and R³ are joined together to form a ring. Non-limiting examples ofamines include isomers of N-methyl-octylamine, isomers ofN-methyl-nonylamine, isomers of N-methyl-decylamine, isomers of Nmethylundecylamine, isomers of N-methyldodecylamine, isomers of N methylteradecylamine, and isomers of N-methyl-hexadecylamine. In certainembodiments, the amine is selected from the group consisting of Nmethyldecylamine and N methylhexadecylamine.

In some embodiments, the amine is of the formula NR¹R²R³, wherein R¹ ismethyl and R² and R³ are the same or different and are cyclic oracyclic, branched or unbranched C₈₋₁₆ alkyl, or optionally R² and R³ arejoined together to form a ring. In some embodiments, the amine is of theformula NR¹R²R³, wherein R¹ is methyl and R² and R³ are the same ordifferent and are cyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl,or optionally R² and R³ are joined together to form a ring. Non-limitingexamples of amines include isomers of N-methyl-N-octyloctylamine,isomers of N-methyl-N-nonylnonylamine, isomers ofN-methyl-N-decyldecylamine, isomers of N-methyl-N-undecylundecylamine,isomers of N-methyl-N-dodecyldodecylamine, isomers ofN-methyl-N-tetradecylteradecylamine, isomers ofN-methyl-N-hexadecylhdexadecylamine, isomers ofN-methyl-N-octylnonylamine, isomers of N-methyl-N-octyldecylamine,isomers of N-methyl-N-octyldodecylamine, isomers ofN-methyl-N-octylundecylamine, isomers ofN-methyl-N-octyltetradecylamine, isomers ofN-methyl-N-octylhexadecylamine, N-methyl-N-nonyldecylamine, isomers ofN-methyl-N-nonyldodecylamine, isomers ofN-methyl-N-nonyltetradecylamine, isomers ofN-methyl-N-nonylhexadecylamine, isomers of N-methyl-N-decyldodecylamine,isomers of N-methyl-N-decylundecylamine, isomers ofN-methyl-N-decyldodecylamine, isomers ofN-methyl-N-decyltetradecylamine, isomers ofN-methyl-N-decylhexadecylamine, isomers ofN-methyl-N-dodecylundecylamine, isomers ofN-methyl-N-dodecyltetradecylamine, isomers ofN-methyl-N-dodecylhexadecylamine, and isomers ofN-methyl-N-tetradecylhexadecylamine. In certain embodiments, the amineis selected from the group consisting of N-methyl-N-octyloctylamine,isomers of N-methyl-N-nonylnonylamine, isomers of N-methylN-decyldecylamine, isomers of N-methyl-N-undecylundecylamine, isomers ofN-methyl-N-dodecyldodecylamine, isomers ofN-methyl-N-tetradecylteradecylamine, and isomers of N-methyl-Nhexadecylhdexadecylamine. In certain embodiments, the amine is selectedfrom the group consisting of N-methyl-N-dodecyldodecylamine and isomersof N-methyl-N hexadecylhexadecylamine. In certain embodiments, the amineis selected from the group consisting of isomers ofN-methyl-N-octylnonylamine, isomers of N-methyl-N-octyldecylamine,isomers of N-methyl-N-octyldodecylamine, isomers ofN-methyl-N-octylundecylamine, isomers ofN-methyl-N-octyltetradecylamine, isomers ofN-methyl-N-octylhexadecylamine, N-methyl-N-nonyldecylamine, isomers ofN-methyl-N-nonyldodecylamine, isomers ofN-methyl-N-nonyltetradecylamine, isomers ofN-methyl-N-nonylhexadecylamine, isomers of N-methyl-N-decyldodecylamine,isomers of N-methyl-N-decylundecylamine, isomers ofN-methyl-N-decyldodecylamine, isomers ofN-methyl-N-decyltetradecylamine, isomers ofN-methyl-N-decylhexadecylamine, isomers ofN-methyl-N-dodecylundecylamine, isomers ofN-methyl-N-dodecyltetradecylamine, isomers ofN-methyl-N-dodecylhexadecylamine, and isomers ofN-methyl-N-tetradecylhexadecylamine. In certain embodiments, the cyclicor acyclic, branched or unbranched tri-substituted amines is selectedfrom the group consisting of N-methyl-N-octyldodecylamine,N-methyl-N-octylhexadecylamine or N-methyl-N-dodecylhexadecylamine.

In certain embodiments, the amine is of the formula NR¹R²R³, wherein R¹and R² are methyl and R³ is cyclic or acyclic, branched or unbranchedC₈₋₁₆ alkyl. Non-limiting examples of amines include isomers ofN,N-dimethylnonylamine, isomers of N,N-dimethyldecylamine, isomers ofN,N-dimethylundecylamine, isomers of N,N-dimethyldodecylamine, isomersof N,N-dimethyltetradecylamine, and isomers ofN,N-dimethylhexadecylamine. In certain embodiments, the amine isselected from the group consisting of N,N-dimethyldecylamine, isomers ofN,N-dodecylamine, and isomers of N,N-dimethylhexadecylamine.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁴, R⁵, and R⁶ are the same or different and are hydrogen or cyclic oracyclic, branched or unbranched alkyl (e.g., C₁₋₁₆ alkyl), optionallysubstituted, or optionally, R⁵ and R⁶ are joined together to form aring. In some embodiments, each of R⁴, R⁵, and R⁶ are the same ordifferent and are hydrogen or cyclic or acyclic, branched or unbranchedalkyl (e.g., C₁₋₁₆ alkyl), optionally substituted, or optionally, R⁵ andR⁶ are joined together to form a ring, provided at least one of R⁴, R⁵,and R⁶ is methyl or ethyl. In some cases, R⁴ is hydrogen or cyclic oracyclic, branched or unbranched C₁-C₆ alkyl, optionally substituted, andR⁵ and R⁶ are the same or different and are hydrogen or cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted, or optionally, R⁵ and R⁶ may be joined together to form aring. In some cases, R⁴ is hydrogen, methyl, or ethyl and R⁵ and R⁶ arethe same or different and are hydrogen or cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), optionally substituted, oroptionally, R⁵ and R⁶ may be joined together to form a ring. In somecases, R⁴ is hydrogen and R⁵ and R⁶ are the same or different and arecyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl),optionally substituted, or optionally, R⁵ and R⁶ may be joined togetherto form a ring. In some cases, R⁴ and R⁵ are the same or different andare hydrogen or cyclic or acyclic, branched or unbranched C₁-C₆ alkyl,optionally substituted, and R⁶ is cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), optionally substituted. In somecases, R⁴ and R⁵ are the same or different and are hydrogen, methyl, orethyl and R⁶ is cyclic or acyclic, branched or unbranched alkyl (e.g.,C₈₋₁₆ alkyl), optionally substituted. In some cases, R⁴ and R⁵ arehydrogen and R⁶ is cyclic or acyclic, branched or unbranched alkyl(e.g., C₈₋₁₆ alkyl), optionally substituted. In some cases, R⁶ ishydrogen or cyclic or acyclic, branched or unbranched C₁-C₆ alkyl,optionally substituted, and R⁴ and R⁵ are the same or different and arehydrogen or cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl), optionally substituted, or optionally. In some cases, R⁶ ishydrogen, methyl, or ethyl and R⁴ and R⁵ are the same or different andare hydrogen or cyclic or acyclic, branched or unbranched alkyl (e.g.,C₈₋₁₆ alkyl). In some cases, R⁶ is hydrogen and R⁴ and R⁵ are the sameor different and are cyclic or acyclic, branched or unbranched alkyl(e.g., C₈₋₁₆ alkyl), optionally substituted. In some cases, R⁵ and R⁶are the same or different and are hydrogen or cyclic or acyclic,branched or unbranched C₁-C₆ alkyl, optionally substituted, and R⁴ iscyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl),optionally substituted. In some cases, R⁵ and R⁶ are the same ordifferent and are hydrogen, methyl, or ethyl and R⁴ is cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted. In some cases, R⁵ and R⁶ are hydrogen and R⁴ is cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁴, R⁵, and R⁶ are the same or different and are cyclic or acyclic,branched or unbranched alkyl (e.g., C₁₋₁₆ alkyl), optionallysubstituted, or optionally, R⁵ and R⁶ are joined together to form aring. In some embodiments, each of R⁴, R⁵, and R⁶ are the same ordifferent and are cyclic or acyclic, branched or unbranched alkyl (e.g.,C₁₋₁₆ alkyl), optionally substituted, or optionally, R⁵ and R⁶ arejoined together to form a ring, provided at least one of R⁴, R⁵, and R⁶is methyl or ethyl. In some cases, R⁴ is cyclic or acyclic, branched orunbranched C₁-C₆ alkyl, optionally substituted, and R⁵ and R⁶ are thesame or different and are hydrogen or cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), optionally substituted, oroptionally, R⁵ and R⁶ may be joined together to form a ring. In somecases, R⁴ is methyl or ethyl and R⁵ and R⁶ are the same or different andare cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl),optionally substituted, or optionally, R⁵ and R⁶ may be joined togetherto form a ring. In some cases, R⁴ is and R⁵ and R⁶ are the same ordifferent and are cyclic or acyclic, branched or unbranched alkyl (e.g.,C₈₋₁₆ alkyl), optionally substituted, or optionally, R⁵ and R⁶ may bejoined together to form a ring. In some cases, R⁴ is methyl and R⁵ andR⁶ are the same or different and are cyclic or acyclic, branched orunbranched alkyl (e.g., C₈₋₁₆ alkyl), optionally substituted, oroptionally, R⁵ and R⁶ may be joined together to form a ring. In somecases, R⁴ and R⁵ are the same or different and are methyl or ethyl andR⁶ is cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl), optionally substituted. In some cases, R⁴ and R⁵ are methyl andR⁶ is cyclic or acyclic, branched or unbranched alkyl (e.g., C₈₋₁₆alkyl), optionally substituted. In some cases, R⁶ is cyclic or acyclic,branched or unbranched C₁-C₆ alkyl, optionally substituted, and R⁴ andR⁵ are the same or different and are hydrogen or cyclic or acyclic,branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted, or optionally. In some cases, R⁶ is methyl or ethyl and R⁴and R⁵ are the same or different and are hydrogen or cyclic or acyclic,branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl). In some cases, R⁶ ismethyl and R⁴ and R⁵ are the same or different and are cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted. In some cases, R⁵ and R⁶ are the same or different and arecyclic or acyclic, branched or unbranched C₁-C₆ alkyl, optionallysubstituted, and R⁴ is cyclic or acyclic, branched or unbranched alkyl(e.g., C₈₋₁₆ alkyl), optionally substituted. In some cases, R⁵ and R⁶are the same or different and are methyl or ethyl and R⁴ is cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted. In some cases, R⁵ and R⁶ are methyl and R⁶ is cyclic oracyclic, branched or unbranched alkyl (e.g., C₈₋₁₆ alkyl), optionallysubstituted.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereineach of R⁴, R⁵, and R⁶ are the same or different and are cyclic oracyclic, branched or unbranched C₄₋₁₆ alkyl, optionally substituted, oroptionally, R⁵ and R⁶ are joined together to form a ring. In someembodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, wherein each ofR⁴, R⁵, and R⁶ are the same or different and are cyclic or acyclic,branched or unbranched C₈₋₁₆ alkyl, optionally substituted, oroptionally, R⁵ and R⁶ are joined together to form a ring. In someembodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, wherein each ofR⁴, R⁵, and R⁶ are the same or different and are selected from the groupconsisting of t-butyl and cyclic or acyclic, branched or unbranchedC₅₋₁₆ alkyl, optionally substituted, or optionally, R⁵ and R⁶ are joinedtogether to form a ring. In some embodiments, R⁴, R⁵, and R⁶ are thesame or different and are selected from the group consisting of t-butyland cyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl, optionallysubstituted, or optionally, R⁵ and R⁶ are joined together to form aring. Non-limiting examples amides include N,N-dioctyloctamide,N,N-dinonylnonamide, N,N-didecyldecamide, N,N-didodecyldodecamide,N,N-diundecylundecamide, N,N-ditetradecyltetradecamide,N,N-dihexadecylhexadecamide, N,N-didecyloctamide, N,N-didodecyloctamide,N,N-dioctyldodecamide, N,N-didecyldodecamide, N,N-dioctylhexadecamide,N,N-didecylhexadecamide, and N,N-didodecylhexadecamide. In certainembodiments, the amide is selected from the group consisting ofN,N-dioctyldodecamide and N,N-didodecyloctamide

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁶ is hydrogen or C₁-C₃ alkyl and R⁴ and R⁵ are the same or differentand are cyclic or acyclic, branched or unbranched C₄₋₁₆ alkyl,optionally substituted. In some embodiments, R⁶ is selected from thegroup consisting of hydrogen, methyl, ethyl, propyl and isopropyl, andR⁴ and R⁵ are the same or different and are cyclic or acyclic, branchedor unbranched C₄₋₁₆ alkyl, optionally substituted. In certainembodiments, R⁶ is selected from the group consisting of hydrogen,methyl, ethyl, propyl and isopropyl, and R⁴ and R⁵ are the same ordifferent and are cyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl,optionally substituted. In some cases, at least one of R⁴ and R⁵ issubstituted with a hydroxy group. In some embodiments, R⁶ is selectedfrom the group consisting of hydrogen, methyl, ethyl, propyl, andisopropyl, and R⁴ and R⁵ are the same or different and are selected fromthe group consisting of tert-butyl, cyclic or acyclic, branched orunbranched C₅₋₁₆ alkyl, optionally substituted, and cyclic or acyclic,branched or unbranched C₁₋₁₆ alkyl substituted with an —OH group.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁶ is C₁-C₃ alkyl and R⁴ and R⁵ are the same or different and are cyclicor acyclic, branched or unbranched C₄₋₁₆ alkyl, optionally substituted.In some embodiments, R⁶ is selected from the group consisting of methyl,ethyl, propyl and isopropyl, and R⁴ and R⁵ are the same or different andare cyclic or acyclic, branched or unbranched C₄₋₁₆ alkyl, optionallysubstituted. In certain embodiments, R⁶ is selected from the groupconsisting of methyl, ethyl, propyl and isopropyl, and R⁴ and R⁵ are thesame or different and are cyclic or acyclic, branched or unbranchedC₈₋₁₆ alkyl, optionally substituted. In some cases, at least one of R⁴and R⁵ is substituted with a hydroxy group. In some embodiments, R⁶ isselected from the group consisting of methyl, ethyl, propyl, andisopropyl, and R⁴ and R⁵ are the same or different and are selected fromthe group consisting of tert-butyl, cyclic or acyclic, branched orunbranched C₅₋₁₆ alkyl, optionally substituted, and cyclic or acyclic,branched or unbranched C₁₋₁₆ alkyl substituted with an —OH group.

Non-limiting examples of amides include N,N-di-tert-butylformamide,N,N-dipentylformamide, N,N-dihexylformamide, N,N-diheptylformamide,N,N-dioctylformamide, N,N-dinonylformamide, N,N-didecylformamide,N,N-diundecylformamide, N,N-didodecylformamide,N,N-dihydroxymethylformamide, N,N-di-tert-butylacetamide,N,N-dipentylacetamide, N,N-dihexylacetamide, N,N-diheptylacetamide,N,N-dioctylacetamide, N,N-dinonylacetamide, N,N-didecylacetamide,N,N-diundecylacetamide, N,N-didodecylacetamide,N,N-dihydroxymethylacetamide, N,N-dimethylpropionamide,N,N-diethylpropionamide, N,N-dipropylpropionamide, such asN,N-di-n-propylpropionamide or N,N-diisopropylpropionamide,N,N-dibutylpropionamide, such as N,N-di-n-butylpropionamide,N,N-di-sec-butylpropionamide, N,N-diisobutylpropionamide orN,N-di-tert-butylpropionamide, N,N-dipentylpropionamide,N,N-dihexylpropionamide, N,N-diheptylpropionamide,N,N-dioctylpropionamide, N,N-dinonylpropionamide,N,N-didecylpropionamide, N,N-diundecylpropionamide,N,N-didodecylpropionamide, N,N-dimethyl-n-butyramide,N,N-diethyl-n-butyramide, N,N-dipropyl-n-butyramide, such asN,N-di-n-propyl-n-butyramide or N,N-diisopropyl-n-butyramide,N,N-dibutyl-n-butyramide, such as N,N-di-n-butyl-n-butyramide,N,N-di-sec-butyl-n-butyramide, N,N-diisobutyl-n-butyramide,N,N-di-tert-butyl-n-butyramide, N,N-dipentyl-n-butyramide,N,N-dihexyl-n-butyramide, N,N-diheptyl-n-butyramide,N,N-dioctyl-n-butyramide, N,N-dinonyl-n-butyramide,N,N-didecyl-n-butyramide, N,N-diundecyl-n-butyramide,N,N-didodecyl-n-butyramide, N,N-dipentylisobutyramide,N,N-dihexylisobutyramide, N,N-diheptylisobutyramide,N,N-dioctylisobutyramide, N,N-dinonylisobutyramide,N,N-didecylisobutyramide, N,N-diundecylisobutyramide,N,N-didodecylisobutyramide, N,N-pentylhexylformamide,N,N-pentylhexylacetamide, N,N-pentylhexylpropionamide,N,N-pentylhexyl-n-butyramide, N,N-pentylhexylisobutyramide,N,N-methylethylpropionamide, N,N-methyl-n-propylpropionamide,N,N-methylisopropylpropionamide, N,N-methyl-n-butylpropionamide,N,N-methylethyl-n-butyramide, N,N-methyl-n-butyramide,N,N-methylisopropyl-n-butyramide, N,N-methyl-n-butyl-n-butyramide,N,N-methylethylisobutyramide, N,N-methyl-n-propylisobutyramide,N,N-methylisopropylisobutyramide, and N,N-methyl-n-butylisobutyramide.In certain embodiments, the amide is selected from the group consistingof N,N-dioctyldodecacetamide,N,N-methyl-N-octylhexadecdidodecylacetamide, andN-methyl-N-ihexadecyldodecylhexadecacetamide.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁶ is hydrogen or methyl and R⁴ and R⁵ are the same or different and arecyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl. Non-limitingamides include isomers of N methyloctamide, isomers of N-methylnonamide,isomers of N-methyldecamide, isomers of N methylundecamide, isomers of Nmethyldodecamide, isomers of N methylteradecamide, and isomers ofN-methyl-hexadecamide. In certain embodiments the amides are selectedfrom the group consisting of N methyloctamide, N methyldodecamide, and Nmethylhexadecamide.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁶ is methyl and R⁴ and R⁵ are the same or different and are cyclic oracyclic, branched or unbranched C₈₋₁₆ alkyl. Non-limiting amides includeisomers of N-methyl-N-octyloctamide, isomers ofN-methyl-N-nonylnonamide, isomers of N-methyl-N-decyldecamide, isomersof N methyl-N undecylundecamide, isomers of Nmethyl-N-dodecyldodecamide, isomers of N methylN-tetradecylteradecamide, isomers of N-methyl-N-hexadecylhdexadecamide,isomers of N-methyl-N-octylnonamide, isomers ofN-methyl-N-octyldecamide, isomers of N-methyl-N-octyldodecamide, isomersof N-methyl-N-octylundecamide, isomers of N-methyl-N-octyltetradecamide,isomers of N-methyl-N-octylhexadecamide, N-methyl-N-nonyldecamide,isomers of N-methyl-N-nonyldodecamide, isomers ofN-methyl-N-nonyltetradecamide, isomers of N-methyl-N-nonylhexadecamide,isomers of N-methyl-N-decyldodecamide, isomers of Nmethyl-N-decylundecamide, isomers of N-methyl-N-decyldodecamide, isomersof N-methyl-N-decyltetradecamide, isomers ofN-methyl-N-decylhexadecamide, isomers of N methyl-N-dodecylundecamide,isomers of N methyl-N-dodecyltetradecamide, isomers ofN-methyl-N-dodecylhexadecamide, and isomers of Nmethyl-N-tetradecylhexadecamide. In certain embodiments, the amide isselected from the group consisting of isomers ofN-methyl-N-octyloctamide, isomers of N-methyl-N-nonylnonamide, isomersof N-methyl-N-decyldecamide, isomers of N methyl-N undecylundecamide,isomers of N methyl-N-dodecyldodecamide, isomers of N methylN-tetradecylteradecamide, and isomers ofN-methyl-N-hexadecylhdexadecamide. In certain embodiments, amide isselected from the group consisting of N-methyl-N-octyloctamide, Nmethyl-N-dodecyldodecamide, and N-methyl-N-hexadecylhexadecamide. Incertain embodiments, the amide is selected from the group consisting ofisomers of N-methyl-N-octylnonamide, isomers ofN-methyl-N-octyldecamide, isomers of N-methyl-N-octyldodecamide, isomersof N-methyl-N-octylundecamide, isomers of N-methyl-N-octyltetradecamide,isomers of N-methyl-N-octylhexadecamide, N-methyl-N-nonyldecamide,isomers of N-methyl-N-nonyldodecamide, isomers ofN-methyl-N-nonyltetradecamide, isomers of N-methyl-N-nonylhexadecamide,isomers of N-methyl-N-decyldodecamide, isomers of Nmethyl-N-decylundecamide, isomers of N-methyl-N-decyldodecamide, isomersof N-methyl-N-decyltetradecamide, isomers ofN-methyl-N-decylhexadecamide, isomers of N methyl-N-dodecylundecamide,isomers of N methyl-N-dodecyltetradecamide, isomers ofN-methyl-N-dodecylhexadecamide, and isomers of Nmethyl-N-tetradecylhexadecamide. In certain embodiments, the amides isselected from the group consisting of N-methyl-N-octyldodecamide,N-methyl-N-octylhexadecamide, and N-methyl-N-dodecylhexadecamide.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁵ and R⁶ are the same or different and are hydrogen or C₁-C₃ alkyl andR⁴ is cyclic or acyclic, branched or unbranched C₄₋₁₆ alkyl, optionallysubstituted. In some embodiments, R⁵ and R⁶ are the same or differentand are selected from the group consisting of hydrogen, methyl, ethyl,propyl and isopropyl, and R⁴ is cyclic or acyclic, branched orunbranched C₄₋₁₆ alkyl, optionally substituted. In certain embodiments,R⁵ and R⁶ are the same or different and are selected from the groupconsisting of hydrogen, methyl, ethyl, propyl and isopropyl and R⁴ iscyclic or acyclic, branched or unbranched C₈₋₁₆ alkyl, optionallysubstituted. In some cases, R⁴ is substituted with a hydroxy group. Insome embodiments, R⁵ and R⁶ are the same or different and are selectedfrom the group consisting of hydrogen, methyl, ethyl, propyl, andisopropyl, and R⁴ is selected from the group consisting of tert-butyl,cyclic or acyclic, branched or unbranched C₅₋₁₆ alkyl, optionallysubstituted, and cyclic or acyclic, branched or unbranched C₁₋₁₆ alkylsubstituted with an —OH group.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁵ and R⁶ are the same or different and are C₁-C₃ alkyl and R⁴ is cyclicor acyclic, branched or unbranched C₄₋₁₆ alkyl, optionally substituted.In some embodiments, R⁵ and R⁶ are the same or different and areselected from the group consisting of methyl, ethyl, propyl andisopropyl, and R⁴ is cyclic or acyclic, branched or unbranched C₄₋₁₆alkyl, optionally substituted. In certain embodiments, R⁵ and R⁶ are thesame or different and are selected from the group consisting of methyl,ethyl, propyl and isopropyl and R⁴ is cyclic or acyclic, branched orunbranched C₈₋₁₆ alkyl, optionally substituted. In some cases, R⁴ issubstituted with a hydroxy group. In some embodiments, R⁵ and R⁶ are thesame or different and are selected from the group consisting of methyl,ethyl, propyl, and isopropyl, and R⁴ is selected from the groupconsisting of tert-butyl, cyclic or acyclic, branched or unbranchedC₅₋₁₆ alkyl, optionally substituted, and cyclic or acyclic, branched orunbranched C₁₋₁₆ alkyl substituted with an —OH group.

In some embodiments, the amide is of the formula N(C═OR⁴)R⁵R⁶, whereinR⁵ and R⁶ are methyl and R⁴ is cyclic or acyclic, branched or unbranchedC₈₋₁₆ alkyl. Non-limiting examples of amides include isomers ofN,N-dimethyloctamide, isomers of N,N-dimethylnonamide, isomers ofN,N-dimethyldecamide, isomers of N,N-dimethylundecamide, isomers ofN,N-dimethyldodecamide, isomers of N,N-dimethyltetradecamide, andisomers of N,N-dimethylhexadecamide. In certain embodiments, the cyclicor acyclic, branched or unbranched tri-substituted amines is selectedfrom the group consisting of N,N-dimethyloctamide, N,N-dodecamide, andN,N-dimethylhexadecamide.

In some embodiments, the solvent is an aromatic solvent having a boilingpoint between about 175-300° F. Non-limiting examples of aromatic liquidsolvents having a boiling point between about 175-300° F. includebenzene, xylenes, and toluene. In a particular embodiment, the solventis not xylene.

I-A3. Fatty Acid Ester Solvents

In some embodiments, at least one of the solvents present in themicroemulsion is an ester of fatty acid, either naturally occurring orsynthetic with the formula R⁷O(C═OR⁸), wherein R⁷ and R⁸ are the same ordifferent and are cyclic or acyclic, branched or unbranched alkyl (e.g.,C1-16 alkyl), optionally substituted. In some embodiments, each of R⁷and R⁸ are the same or different and are cyclic or acyclic, branched orunbranched alkyl, or optionally, provide at least one of R⁷ and R⁸ ismethyl, ethyl, propyl, or butyl. Non-limiting examples include isomersof methyl octanoate, methyl decanoate, methyl dodecanoate, methylundecanoate, methyl hexadecanoate, ethyl octanoate, ethyl decanoate,ethyl dodecanoate, ethyl undecanoate, ethyl hexadecanoate, propyloctanoate, propyl decanoate, propyl dodecanoate, propyl undecanoate,propyl hexadecanoate, butyl octanoate, butyl decanoate, butyldodecanoate, butyl undecanoate, and butyl hexadecanoate. In certainembodiments, the esters are selected from the group consisting of methyldodecanoate, methyl hexadecanoate, ethyl dodecanoate, ethylhexadecanoate, propyl dodecanoate, propyl hexadecanoate, butyldodecanoate, and butyl hexadecanoate. Non-limiting examples includeisomers of octyl octanoate, nonyl, nonanoate, decyl decanoate, undecylundecanoate, dodecyl decanoate, hexadecyl hexadecanoate. In certainembodiments the esters are selected from the group consisting of octyloctonoate and decyl decanoate.

I-A4. Terpene Solvents

In some embodiments, at least one of the solvents present in themicroemulsion is a terpene or a terpenoid. In some embodiments, theterpene or terpenoid comprises a first type of terpene or terpenoid anda second type of terpene or terpenoid. Terpenes may be generallyclassified as monoterpenes (e.g., having two isoprene units),sesquiterpenes (e.g., having 3 isoprene units), diterpenes, or the like.The term terpenoid also includes natural degradation products, such asionones, and natural and synthetic derivatives, e.g., terpene alcohols,aldehydes, ketones, acids, esters, epoxides, and hydrogenation products(e.g., see Ullmann's Encyclopedia of Industrial Chemistry, 2012, pages29-45, herein incorporated by reference). It should be understood, thatwhile much of the description herein focuses on terpenes, this is by nomeans limiting, and terpenoids may be employed where appropriate. Insome cases, the terpene is a naturally occurring terpene. In some cases,the terpene is a non-naturally occurring terpene and/or a chemicallymodified terpene (e.g., saturated terpene, terpene amine, fluorinatedterpene, or silylated terpene).

In some embodiments, the terpene is a monoterpene. Monoterpenes may befurther classified as acyclic, monocyclic, and bicyclic (e.g., with atotal number of carbons in the range between 18-20), as well as whetherthe monoterpene comprises one or more oxygen atoms (e.g., alcoholgroups, ester groups, carbonyl groups, etc.). In some embodiments, theterpene is an oxygenated terpene, for example, a terpene comprising analcohol, an aldehyde, and/or a ketone group. In some embodiments, theterpene comprises an alcohol group. Non-limiting examples of terpenescomprising an alcohol group are linalool, geraniol, nopol, α-terpineol,and menthol. In some embodiments, the terpene comprises an ether-oxygen,for example, eucalyptol, or a carbonyl oxygen, for example, menthone. Insome embodiments, the terpene does not comprise an oxygen atom, forexample, d-limonene.

Non-limiting examples of terpenes include linalool, geraniol, nopol,α-terpineol, menthol, eucalyptol, menthone, d-limonene, terpinolene,β-occimene, γ-terpinene, α-pinene, and citronellene. In a particularembodiment, the terpene is selected from the group consisting ofα-terpeneol, α-pinene, nopol, and eucalyptol. In one embodiment, theterpene is nopol. In another embodiment, the terpene is eucalyptol. Insome embodiments, the terpene is not limonene (e.g., d-limonene). Insome embodiments, the emulsion is free of limonene.

In some embodiments, the terpene is a non-naturally occurring terpeneand/or a chemically modified terpene (e.g., saturated terpene). In somecases, the terpene is a partially or fully saturated terpene (e.g.,p-menthane, pinane). In some cases, the terpene is a non-naturallyoccurring terpene. Non-limiting examples of non-naturally occurringterpenes include, menthene, p-cymene, r-carvone, terpinenes (e.g.,alpha-terpinenes, beta-terpinenes, gamma-terpinenes), dipentenes,terpinolenes, borneol, alpha-terpinamine, and pine oils.

In some embodiments, the terpene is classified in terms of its phaseinversion temperature (PIT). The term phase inversion temperature isgiven its ordinary meaning in the art and refers to the temperature atwhich an oil in water microemulsion inverts to a water in oilmicroemulsion (or vice versa). Those of ordinary skill in the art willbe aware of methods for determining the PIT for a microemulsioncomprising a terpene (e.g., see Strey, Colloid & Polymer Science, 1994.272(8): p. 1005-1019; Kahlweit et al., Angewandte Chemie InternationalEdition in English, 1985. 24(8): p. 654-668). The PIT values describedherein were determined using a 1:1 ratio of terpene (e.g., one or moreterpenes):de-ionized water and varying amounts (e.g., between about 20wt % and about 60 wt %; generally, between 3 and 9 different amounts areemployed) of a 1:1 blend of surfactant comprising linear C₁₂-C₁₅ alcoholethoxylates with on average 7 moles of ethylene oxide (e.g., Neodol25-7):isopropyl alcohol wherein the upper and lower temperatureboundaries of the microemulsion region can be determined and a phasediagram may be generated. Those of ordinary skill in the art willrecognize that such a phase diagram (e.g., a plot of temperature againstsurfactant concentration at a constant oil-to-water ratio) may bereferred to as fish diagram or a Kahlweit plot. The temperature at thevertex is the PIT. An exemplary fish diagram indicating the PIT is shownin FIG. 1. PITs for non-limiting examples of terpenes determined usingthis experimental procedure outlined above are given in Table 1.

TABLE 1 Phase inversion temperatures for non-limiting examples ofterpenes. Phase Inversion Temperature Terpene ° F. (° C.) linalool 24.8(−4) geraniol 31.1 (−0.5) nopol 36.5 (2.5) α-terpineol 40.3 (4.6)menthol 60.8 (16) eucalyptol 87.8 (31) menthone 89.6 (32) d-limonene109.4 (43) terpinolene 118.4 (48) β-occimene 120.2 (49) γ-terpinene120.2 (49) α-pinene 134.6 (57) citronellene 136.4 (58)I-A5. Crude Cut Solvents

In certain embodiments, the solvent utilized in the emulsion ormicroemulsion herein may comprise one or more impurities. For example,in some embodiments, a solvent (e.g., a terpene) is extracted from anatural source (e.g., citrus, pine), and may comprise one or moreimpurities present from the extraction process. In some embodiment, thesolvent comprises a crude cut (e.g., uncut crude oil, for example, madeby settling, separation, heating, etc.). In some embodiments, thesolvent is a crude oil (e.g., naturally occurring crude oil, uncut crudeoil, crude oil extracted from the wellbore, synthetic crude oil, crudecitrus oil, crude pine oil, eucalyptus, etc.). In some embodiments, thesolvent is a citrus extract (e.g., crude orange oil, orange oil, etc.).

I-A6. Mutual Solvents

In some embodiments, at least one of the solvents comprised in theemulsion or microemulsion comprising a mutual solvent which is miscibletogether with the water and the solvent. In some embodiments, the mutualsolvent is present in an amount between about at 0.5 wt % to about 30%of mutual solvent. Non-limiting examples of suitable mutual solventsinclude ethyleneglycolmonobutyl ether (EGMBE), dipropylene glycolmonomethyl ether, short chain alcohols (e.g., isopropanol),tetrahydrofuran, dioxane, dimethylformamide, and dimethylsulfoxide.

I-B. Aqueous Phase

Generally, the microemulsion comprises an aqueous phase. Generally, theaqueous phase comprises water. The water may be provided from anysuitable source (e.g., sea water, fresh water, deionized water, reverseosmosis water, water from field production). The water may be present inany suitable amount. In some embodiments, the total amount of waterpresent in the microemulsion is between about 1 wt % about 95 wt %, orbetween about 1 wt % about 90 wt %, or between about 1 wt % and about 60wt %, or between about 5 wt % and about 60 wt % or between about 10 andabout 55 wt %, or between about 15 and about 45 wt %, versus the totalmicroemulsion composition.

The water to solvent ratio in a microemulsion may be varied. In someembodiments, the ratio of water to solvent, along with other parametersof the solvent may be varied. In some embodiments, the ratio of water tosolvent by weight is between about 15:1 and 1:10, or between 9:1 and1:4, or between 3.2:1 and 1:4.

I-C. Surfactants

In some embodiments, the microemulsion comprises a surfactant. Themicroemulsion may comprise a single surfactant or a combination of twoor more surfactants. For example, in some embodiments, the surfactantcomprises a first type of surfactant and a second type of surfactant.The term surfactant, as used herein, is given its ordinary meaning inthe art and refers to compounds having an amphiphilic structure whichgives them a specific affinity for oil/water-type and water/oil-typeinterfaces which helps the compounds to reduce the free energy of theseinterfaces and to stabilize the dispersed phase of a microemulsion. Theterm surfactant encompasses cationic surfactants, anionic surfactants,amphoteric surfactants, nonionic surfactants, zwitterionic surfactants,and mixtures thereof. In some embodiments, the surfactant is a nonionicsurfactant. Nonionic surfactants generally do not contain any charges.Amphoteric surfactants generally have both positive and negativecharges, however, the net charge of the surfactant can be positive,negative, or neutral, depending on the pH of the solution. Anionicsurfactants generally possess a net negative charge. Cationicsurfactants generally possess a net positive charge. Zwitterionicsurfactants are generally not pH dependent. A zwitterion is a neutralmolecule with a positive and a negative electrical charge, thoughmultiple positive and negative charges can be present. Zwitterions aredistinct from dipole, at different locations within that molecule.

In some embodiments, the surfactant is an amphiphilic block copolymerwhere one block is hydrophobic and one block is hydrophilic. In somecases, the total molecular weight of the polymer is greater than 5000daltons. The hydrophilic block of these polymers can be nonionic,anionic, cationic, amphoteric, or zwitterionic.

The term surface energy, as used herein, is given its ordinary meaningin the art and refers to the extent of disruption of intermolecularbonds that occur when the surface is created (e.g., the energy excessassociated with the surface as compared to the bulk). Generally, surfaceenergy is also referred to as surface tension (e.g., for liquid-gasinterfaces) or interfacial tension (e.g., for liquid-liquid interfaces).As will be understood by those skilled in the art, surfactants generallyorient themselves across the interface to minimize the extent ofdisruption of intermolecular bonds (i.e. lower the surface energy).Typically, a surfactant at an interface between polar and non-polarphases orient themselves at the interface such that the difference inpolarity is minimized.

Those of ordinary skill in the art will be aware of methods andtechniques for selecting surfactants for use in the microemulsionsdescribed herein. In some cases, the surfactant(s) are matched to and/oroptimized for the particular oil or solvent in use. In some embodiments,the surfactant(s) are selected by mapping the phase behavior of themicroemulsion and choosing the surfactant(s) that gives the desiredrange of phase behavior. In some cases, the stability of themicroemulsion over a wide range of temperatures is targeted as themicroemulsion may be subject to a wide range of temperatures due to theenvironmental conditions present at the subterranean formation and/orreservoir.

The surfactant may be present in the microemulsion in any suitableamount. In some embodiments, the surfactant is present in an amountbetween about 0 wt % and about 99 wt %, or between about 1 wt % andabout 90 wt %, or between about 0 wt % and about 60 wt %, or betweenabout 1 wt % and about 60 wt %, or between about 5 wt % and about 60 wt%, or between about 10 wt % and about 60 wt %, or between about 5 wt %and about 65 wt %, or between about 5 wt % and about 55 wt %, or betweenabout 10 wt % and about 55 wt %, or between about 2 wt % and about 50 wt%, or between about 0 wt % and about 40 wt %, or between about 15 wt %and about 55 wt %, or between about 20 wt % and about 50 wt %, versusthe total microemulsion composition.

Suitable surfactants for use with the compositions and methods describedherein will be known in the art. In some embodiments, the surfactant isan alkyl polyglycol ether, for example, having 2-250 ethylene oxide (EO)(e.g., or 2-200, or 2-150, or 2-100, or 2-50, or 2-40) units and alkylgroups of 4-20 carbon atoms. In some embodiments, the surfactant is analkylaryl polyglycol ether having 2-250 EO units (e.g., or 2-200, or2-150, or 2-100, or 2-50, or 2-40) and 8-20 carbon atoms in the alkyland aryl groups. In some embodiments, the surfactant is an ethyleneoxide/propylene oxide (EO/PO) block copolymer having 2-250 EO or POunits (e.g., or 2-200, or 2-150, or 2-100, or 2-50, or 2-40). In someembodiments, the surfactant is a fatty acid polyglycol ester having 6-24carbon atoms and 2-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or2-50, or 2-40). In some embodiments, the surfactant is a polyglycolether of hydroxyl-containing triglycerides (e.g., castor oil). In someembodiments, the surfactant is an alkylpolyglycoside of the generalformula R″—O—Z_(n), where R″ denotes a linear or branched, saturated orunsaturated alkyl group having on average 8-24 carbon atoms and Z_(n)denotes an oligoglycoside group having on average n=1-10 hexose orpentose units or mixtures thereof. In some embodiments, the surfactantis a fatty ester of glycerol, sorbitol, or pentaerythritol. In someembodiments, the surfactant is an amine oxide (e.g.,dodecyldimethylamine oxide). In some embodiments, the surfactant is analkyl sulfate, for example having a chain length of 8-18 carbon atoms,alkyl ether sulfates having 8-18 carbon atoms in the hydrophobic groupand 1-40 ethylene oxide (EO) or propylene oxide (PO) units. In someembodiments, the surfactant is a sulfonate, for example, an alkylsulfonate having 8-18 carbon atoms, an alkylaryl sulfonate having 8-18carbon atoms, an ester or half ester of sulfosuccinic acid withmonohydric alcohols or alkylphenols having 4-15 carbon atoms, or amultisulfonate (e.g., comprising two, three, four, or more, sulfonategroups). In some cases, the alcohol or alkylphenol can also beethoxylated with 1-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or2-50, or 2-40). In some embodiments, the surfactant is an alkali metalsalt or ammonium salt of a carboxylic acid or poly(alkylene glycol)ether carboxylic acid having 8-20 carbon atoms in the alkyl, aryl,alkaryl or aralkyl group and 1-250 EO or PO units (e.g., or 2-200, or2-150, or 2-100, or 2-50, or 2-40). In some embodiments, the surfactantis a partial phosphoric ester or the corresponding alkali metal salt orammonium salt, e.g., an alkyl and alkaryl phosphate having 8-20 carbonatoms in the organic group, an alkylether phosphate or alkaryletherphosphate having 8-20 carbon atoms in the alkyl or alkaryl group and1-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or 2-50, or 2-40).In some embodiments, the surfactant is a salt of primary, secondary, ortertiary fatty amine having 8-24 carbon atoms with acetic acid, sulfuricacid, hydrochloric acid, and phosphoric acid. In some embodiments, thesurfactant is a quaternary alkyl- and alkylbenzylammonium salt, whosealkyl groups have 1-24 carbon atoms (e.g., a halide, sulfate, phosphate,acetate, or hydroxide salt). In some embodiments, the surfactant is analkylpyridinium, an alkylimidazolinium, or an alkyloxazolinium saltwhose alkyl chain has up to 18 carbons atoms (e.g., a halide, sulfate,phosphate, acetate, or hydroxide salt). In some embodiments, thesurfactant is amphoteric or zwitterionic, including sultaines (e.g.,cocamidopropyl hydroxysultaine), betaines (e.g., cocamidopropylbetaine), or phosphates (e.g., lecithin). Non-limiting examples ofspecific surfactants include a linear C₁₂-C₁₅ ethoxylated alcohols with5-12 moles of EO, lauryl alcohol ethoxylate with 4-8 moles of EO, nonylphenol ethoxylate with 5-9 moles of EO, octyl phenol ethoxylate with 5-9moles of EO, tridecyl alcohol ethoxylate with 5-9 moles of EO, Pluronic®matrix of EO/PO copolymers, ethoxylated cocoamide with 4-8 moles of EO,ethoxylated coco fatty acid with 7-11 moles of EO, and cocoamidopropylamine oxide.

In some embodiments, the surfactant is a siloxane surfactant asdescribed in U.S. patent application Ser. No. 13/831,410, filed Mar. 14,2014, herein incorporated by reference.

In some embodiments, the surfactant is a Gemini surfactant. Geminisurfactants generally have the structure of multiple amphiphilicmolecules linked together by one or more covalent spacers. In someembodiments, the surfactant is an extended surfactant, wherein theextended surfactants has the structure where a non-ionic hydrophilicspacer (e.g. ethylene oxide or propylene oxide) connects an ionichydrophilic group (e.g. carboxylate, sulfate, phosphate).

In some embodiments the surfactant is an alkoxylated polyimine with arelative solubility number (RSN) in the range of 5-20. As will be knownto those of ordinary skill in the art, RSN values are generallydetermined by titrating water into a solution of surfactant in1,4dioxane. The RSN values is generally defined as the amount ofdistilled water necessary to be added to produce persistent turbidity.In some embodiments the surfactant is an alkoxylated novolac resin (alsoknown as a phenolic resin) with a relative solubility number in therange of 5-20. In some embodiments the surfactant is a block copolymersurfactant with a total molecular weight greater than 5000 daltons. Theblock copolymer may have a hydrophobic block that is comprised of apolymer chain that is linear, branched, hyperbranched, dendritic orcyclic. Non-limiting examples of monomeric repeat units in thehydrophobic chains of block copolymer surfactants are isomers ofacrylic, methacrylic, styrenic, isoprene, butadiene, acrylamide,ethylene, propylene and norbornene. The block copolymer may have ahydrophilic block that is comprised of a polymer chain that is linear,branched, hyper branched, dendritic or cyclic. Non-limiting examples ofmonomeric repeat units in the hydrophilic chains of the block copolymersurfactants are isomers of acrylic acid, maleic acid, methacrylic acid,ethylene oxide, and acrylamine.

In some embodiments, the surfactant has a structure as in Formula I:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, R¹² is hydrogen oralkyl, n is 1-100, and each m is independently 1 or 2. In someembodiments, Ar is phenyl. In some embodiments, for a compound ofFormula (I), R¹² is hydrogen or C₁₋₆ alkyl. In some embodiments, for acompound of Formula (I), R¹² is H, methyl, or ethyl. In someembodiments, for a compound of Formula (I), R¹² is H.

In some embodiments, the surfactant has a structure as in Formula II:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, Y⁻ is an anionicgroup, X⁺ is a cationic group, n is 1-100, and each m is independently 1or 2. In some embodiments, Ar is phenyl. In some embodiments, for acompound of Formula (II), X⁺ is a metal cation or N(R¹³)₄, wherein eachR¹³ is independently selected from the group consisting of hydrogen,optionally substituted alkyl, or optionally substituted aryl. In someembodiments, X⁺ is NH₄. Non-limiting examples of metal cations are Na⁺,K⁺, Mg⁺², and Ca⁺². In some embodiments, for a compound of Formula (II),Y⁻ is —O⁻, —SO₂O⁻, or —OSO₂O⁻.

In some embodiments, the surfactant has a structure as in Formula III:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, Z⁺ is a cationicgroup, n is 1-100, and each m is independently 1 or 2. In someembodiments, Ar is phenyl. In some embodiments, for a compound ofFormula (III), Z⁺ is N(R¹³)₃, wherein each R¹³ is independent selectedfrom the group consisting of hydrogen, optionally substituted alkyl, oroptionally substituted aryl.

In some embodiments, for a compound of Formula (I), (II), or (III), twoof R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr. In some embodiments, for acompound of Formula (I), (II), or (III), one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹is —CH═CHAr and each of the other groups is hydrogen. In someembodiments, for a compound of Formula (I), (II), or (III), two of R⁷,R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr and each of the other groups ishydrogen. In some embodiments, for a compound of Formula (I), (II), or(III), R⁷ and R⁸ are —CH═CHAr and R⁹, R¹⁰, and R¹¹ are each hydrogen. Insome embodiments, for a compound of Formula (I), (II), or (III), threeof R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr and each of the other groups ishydrogen. In some embodiments, for a compound of Formula (I), (II), or(III), R⁷, R⁸, and R⁹ are —CH═CHAr and R¹⁰ and R¹¹ are each hydrogen. Inembodiments, for a compound of Formula (I), (II), or (III), Ar isphenyl. In some embodiments, for a compound of Formula (I), (II), or(III), each m is 1. In some embodiments, for a compound of Formula (I),(II), or (III), each m is 2. In some embodiments, for a compound ofFormula (I), (II), or (III), n is 6-100, or 1-50, or 6-50, or 6-25, or1-25, or 5-50, or 5-25, or 5-20.

In some embodiments, an emulsion or microemulsion comprises a surfactantof Formula (I), (II), or (III) in an amount between about 1 wt % andabout 20 wt %, or between about 3 wt % and about 15 wt %, or betweenabout 5 wt % and about 13 wt %, or between about 5 wt % and about 11 wt%, or between about 7 wt % and about 11 wt %, or between about 10 wt %and about 12 wt %, or between about 8 wt % and about 12 wt %, or betweenabout 8 wt % and about 10 wt %, or about 9 wt %. In some embodiments,the emulsion or microemulsion comprises, in addition to the surfactantof Formula (I), (II), or (III), water and a non-aqueous phase (e.g., aterpene), and optionally other additives (e.g., one or more additionalsurfactants, an alcohol, a freezing point depression agent, etc.). Insome embodiments, the emulsion or microemulsion comprises, in additionto the surfactant of Formula (I), (II), or (III), water, a terpene, analcohol, one or more additional surfactants, and optionally otheradditives (e.g., a freezing point depression agent). In someembodiments, the emulsion or microemulsion comprises, in addition to thesurfactant of Formula (I), (II), or (III), between about 20 wt % and 90wt % water, between about 2 wt % and about 70 wt % of one or moreadditional surfactants, between about 1 wt % and about 80 wt % of asolvent (e.g., terpene), and between about 10 wt % and about 40 wt % ofa mutual solvent (e.g., alcohol). In some embodiments, the emulsion ormicroemulsion comprises, in addition to the surfactant of Formula (I),(II), or (III), between about 10 wt % and 80 wt % water, between about 2wt % and about 80 wt % of one or more additional surfactants, betweenabout 1 wt % and about 70 wt % of a solvent (e.g., terpene), and betweenabout 5 wt % and about 40 wt % of a mutual solvent (e.g., alcohol). Insome embodiments, the emulsion or microemulsion comprises, in additionto the surfactant of Formula (I), (II), or (III), between about 20 wt %and 90 wt % water, between about 2 wt % and about 70 wt % of one or moreadditional surfactants, between about 1 wt % and about 78 wt % of asolvent (e.g., terpene), and between about 22 wt % and about 40 wt % ofa mutual solvent (e.g., alcohol). Non-limiting examples of surfactantsof Formula (I), (II), or (III) include styrylphenol ethoxylate, atristyrylphenol ethoxylate, a styrylphenol propoxylate, atristyrylphenol propoxylate, a styrylphenol ethoxylate propoxylate, or atristyrylphenol ethoxylate propoxylate.

I-D. Additives

In some embodiments, the emulsion or microemulsion may comprise one ormore additives in addition to water, solvent (e.g., one or more types ofsolvents), and surfactant (e.g., one or more types of surfactants). Insome embodiments, the additive is an alcohol, a freezing pointdepression agent, an acid, a salt, a proppant, a scale inhibitor, afriction reducer, a biocide, a corrosion inhibitor, a buffer, aviscosifier, a clay swelling inhibitor, an oxygen scavenger, and/or aclay stabilizer.

I-D1. Alcohol

In some embodiments, the microemulsion comprises an alcohol. The alcoholmay serve as a coupling agent between the solvent and the surfactant andaid in the stabilization of the microemulsion. The alcohol may alsolower the freezing point of the microemulsion. The microemulsion maycomprise a single alcohol or a combination of two or more alcohols. Insome embodiments, the alcohol is selected from primary, secondary andtertiary alcohols having between 1 and 20 carbon atoms. In someembodiments, the alcohol comprises a first type of alcohol and a secondtype of alcohol. Non-limiting examples of alcohols include methanol,ethanol, isopropanol, n-propanol, n-butanol, i-butanol, sec-butanol,iso-butanol, and t-butanol. In some embodiments, the alcohol is ethanolor isopropanol. In some embodiments, the alcohol is isopropanol.

The alcohol may be present in the emulsion in any suitable amount. Insome embodiments, the alcohol is present in an amount between about 0 wt% and about 50 wt %, or between about 0.1 wt % and about 50 wt %, orbetween about 1 wt % and about 50 wt %, or between about 2 wt % andabout 50 wt % or between about 5 wt % and about 40 wt %, or betweenabout 5 wt % and 35 wt %, versus the total microemulsion composition.

I-D2. Freezing Point Depression Agents

In some embodiments, the microemulsion comprises a freezing pointdepression agent. The microemulsion may comprise a single freezing pointdepression agent or a combination of two or more freezing pointdepression agents. For example, in some embodiments, the freezing pointdepression agent comprises a first type of freezing point depressionagent and a second type of freezing point depression agent. The termfreezing point depression agent is given its ordinary meaning in the artand refers to a compound which is added to a solution to reduce thefreezing point of the solution. That is, a solution comprising thefreezing point depression agent has a lower freezing point as comparedto an essentially identical solution not comprising the freezing pointdepression agent. Those of ordinary skill in the art will be aware ofsuitable freezing point depression agents for use in the microemulsionsdescribed herein. Non-limiting examples of freezing point depressionagents include primary, secondary, and tertiary alcohols with between 1and 20 carbon atoms. In some embodiments, the alcohol comprises at least2 carbon atoms, alkylene glycols including polyalkylene glycols, andsalts. Non-limiting examples of alcohols include methanol, ethanol,i-propanol, n-propanol, t-butanol, n-butanol, n-pentanol, n-hexanol, and2-ethyl-hexanol. In some embodiments, the freezing point depressionagent is not methanol (e.g., due to toxicity). Non-limiting examples ofalkylene glycols include ethylene glycol (EG), polyethylene glycol(PEG), propylene glycol (PG), and triethylene glycol (TEG). In someembodiments, the freezing point depression agent is not ethylene oxide(e.g., due to toxicity). In some embodiments, the freezing pointdepression agent comprises an alcohol and an alkylene glycol. In someembodiments, the freezing point depression agent comprises acarboxycyclic acid salt and/or a di-carboxycylic acid salt. Anothernon-limiting example of a freezing point depression agent is acombination of choline chloride and urea. In some embodiments, themicroemulsion comprising the freezing point depression agent is stableover a wide range of temperatures, for example, between about −50° F. to200° F.

The freezing point depression agent may be present in the microemulsionin any suitable amount. In some embodiments, the freezing pointdepression agent is present in an amount between about 0 wt % and about70 wt %, or between about 0.5 and 30 wt %, or between about 1 wt % andabout 40 wt %, or between about 0 wt % and about 25 wt %, or betweenabout 1 wt % and about 25 wt %, or between about 1 wt % and about 20 wt%, or between about 3 wt % and about 20 wt %, or between about 8 wt %and about 16 wt %, versus the total microemulsion composition.

I-E. Other Additives

In addition to the alcohol and the freezing point depression agent, themicroemulsion may comprise other additives. For example, themicroemulsion may comprise an acid and/or a salt. Further non-limitingexamples of other additives include proppants, scale inhibitors,friction reducers, biocides, corrosion inhibitors, buffers,viscosifiers, clay swelling inhibitors, paraffin dispersing additives,asphaltene dispersing additives, and oxygen scavengers.

Non-limiting examples of proppants (e.g., propping agents) includegrains of sand, glass beads, crystalline silica (e.g., Quartz),hexamethylenetetramine, ceramic proppants (e.g., calcined clays), resincoated sands, and resin coated ceramic proppants. Other proppants arealso possible and will be known to those skilled in the art.

Non-limiting examples of scale inhibitors include one or more of methylalcohol, organic phosphonic acid salts (e.g., phosphonate salt),polyacrylate, ethane-1,2-diol, calcium chloride, and sodium hydroxide.Other scale inhibitors are also possible and will be known to thoseskilled in the art.

Non-limiting examples of buffers include acetic acid, acetic anhydride,potassium hydroxide, sodium hydroxide, and sodium acetate. Other buffersare also possible and will be known to those skilled in the art.

Non-limiting examples of corrosion inhibitors include isopropanol,quaternary ammonium compounds, thiourea/formaldehyde copolymers,propargyl alcohol and methanol. Other corrosion inhibitors are alsopossible and will be known to those skilled in the art.

Non-limiting examples of biocides include didecyl dimethyl ammoniumchloride, gluteral, Dazomet, bronopol, tributyl tetradecyl phosphoniumchloride, tetrakis (hydroxymethyl) phosphonium sulfate, AQUCAR™,UCARCIDE™, glutaraldehyde, sodium hypochlorite, and sodium hydroxide.Other biocides are also possible and will be known to those skilled inthe art.

Non-limiting examples of clay swelling inhibitors include quaternaryammonium chloride and tetramethylammonium chloride. Other clay swellinginhibitors are also possible and will be known to those skilled in theart.

Non-limiting examples of friction reducers include petroleumdistillates, ammonium salts, polyethoxylated alcohol surfactants, andanionic polyacrylamide copolymers. Other friction reducers are alsopossible and will be known to those skilled in the art.

Non-limiting examples of oxygen scavengers include sulfites, andbisulfites. Other oxygen scavengers are also possible and will be knownto those skilled in the art.

Non-limiting examples of paraffin dispersing additives and asphaltenedispersing additives include active acidic copolymers, active alkylatedpolyester, active alkylated polyester amides, active alkylated polyesterimides, aromatic naphthas, and active amine sulfonates. Other paraffindispersing additives are also possible and will be known to thoseskilled in the art.

In some embodiments, for the formulations above, the other additives arepresent in an amount between about 0 wt % about 70 wt %, or betweenabout 0 wt % and about 30 wt %, or between about 1 wt % and about 30 wt%, or between about 1 wt % and about 25 wt %, or between about 1 andabout 20 wt %, versus the total microemulsion composition.

I-E1. Acids

In some embodiments, the microemulsion comprises an acid or an acidprecursor. For example, the microemulsion may comprise an acid when usedduring acidizing operations. The microemulsion may comprise a singleacid or a combination of two or more acids. For example, in someembodiments, the acid comprises a first type of acid and a second typeof acid. Non-limiting examples of acids or di-acids include hydrochloricacid, acetic acid, formic acid, succinic acid, maleic acid, malic acid,lactic acid, and hydrochloric-hydrofluoric acids. In some embodiments,the microemulsion comprises an organic acid or organic di-acid in theester (or di-ester) form, whereby the ester (or diester) is hydrolyzedin the wellbore and/or reservoir to form the parent organic acid and analcohol in the wellbore and/or reservoir. Non-limiting examples ofesters or di-esters include isomers of methyl formate, ethyl formate,ethylene glycol diformate,α,α-4-trimethyl-3-cyclohexene-1-methylformate, methyl lactate, ethyllactate, α,α-4-trimethyl 3-cyclohexene-1-methyllactate, ethylene glycoldilactate, ethylene glycol diacetate, methyl acetate, ethyl acetate,α,α,-4-trimethyl-3-cyclohexene-1-methylacetate, dimethyl succinate,dimethyl maleate, di(α,α-4-trimethyl-3-cyclohexene-1-methyl)succinate,1-methyl-4-(1-methylethenyl)-cyclohexylformate,1-methyl-4-(1-ethylethenyl)cyclohexylactate,1-methyl-4-(1-methylethenyl)cyclohexylacetate,di(1-methy-4-(1-methylethenyl)cyclohexyl)succinate.

I-E2. Salts

In some embodiments, the microemulsion comprises a salt. The presence ofthe salt may reduce the amount of water needed as a carrier fluid, andin addition, may lower the freezing point of the microemulsion. Themicroemulsion may comprise a single salt or a combination of two or moresalts. For example, in some embodiments, the salt comprises a first typeof salt and a second type of salt. Non-limiting examples of saltsinclude salts comprising K, Na, Br, Cr, Cs, or Li, for example, halidesof these metals, including NaCl, KCl, CaCl₂, and MgCl₂.

In some embodiments, the microemulsion comprises a clay stabilizer. Themicroemulsion may comprise a single clay stabilizer or a combination oftwo or more clay stabilizers. For example, in some embodiments, the saltcomprises a first type of clay stabilizer and a second type of claystabilizer. Non-limiting examples of clay stabilizers include saltsabove, polymers (PAC, PHPA, etc), glycols, sulfonated asphalt, lignite,sodium silicate, and choline chloride.

I-F. Formation and Use of Microemulsions

In some embodiments, the components of the microemulsion and/or theamounts of the components are selected such that the microemulsion isstable over a wide-range of temperatures. For example, the microemulsionmay exhibit stability between about −40° F. and about 400° F., orbetween about −40° F. and about 300° F. or between about −40° F. andabout 150° F. Those of ordinary skill in the art will be aware ofmethods and techniques for determining the range of stability of themicroemulsion. For example, the lower boundary may be determined by thefreezing point and the upper boundary may be determined by the cloudpoint and/or using spectroscopy methods. Stability over a wide range oftemperatures may be important in embodiments where the microemulsionsare being employed in applications comprising environments wherein thetemperature may vary significantly, or may have extreme highs (e.g.,desert) or lows (e.g., artic).

The microemulsions described herein may be formed using methods known tothose of ordinary skill in the art. In some embodiments, the aqueous andnon-aqueous phases may be combined (e.g., the water and the solvent(s)),followed by addition of a surfactant(s) and optionally (e.g., freezingpoint depression agent(s)) and agitation. The strength, type, and lengthof the agitation may be varied as known in the art depending on variousfactors including the components of the microemulsion, the quantity ofthe microemulsion, and the resulting type of microemulsion formed. Forexample, for small samples, a few seconds of gentle mixing can yield amicroemulsion, whereas for larger samples, longer agitation times and/orstronger agitation may be required. Agitation may be provided by anysuitable source, for example, a vortex mixer, a stirrer (e.g., magneticstirrer), etc.

Any suitable method for injecting the microemulsion (e.g., a dilutedmicroemulsion) into a wellbore may be employed. For example, in someembodiments, the microemulsion, optionally diluted, may be injected intoa subterranean formation by injecting it into a well or wellbore in thezone of interest of the formation and thereafter pressurizing it intothe formation for the selected distance. Methods for achieving theplacement of a selected quantity of a mixture in a subterraneanformation are known in the art. The well may be treated with themicroemulsion for a suitable period of time. The microemulsion and/orother fluids may be removed from the well using known techniques,including producing the well.

It should be understood, that in embodiments where a microemulsion issaid to be injected into a wellbore, that the microemulsion may bediluted and/or combined with other liquid component(s) prior to and/orduring injection (e.g., via straight tubing, via coiled tubing, etc.).For example, in some embodiments, the microemulsion is diluted with anaqueous carrier fluid (e.g., water, brine, sea water, fresh water, or awell-treatment fluid (e.g., an acid, a fracturing fluid comprisingpolymers, produced water, sand, slickwater, etc.,)) prior to and/orduring injection into the wellbore. In some embodiments, a compositionfor injecting into a wellbore is provided comprising a microemulsion asdescribed herein and an aqueous carrier fluid, wherein the microemulsionis present in an amount between about 0.1 and about 50 gallons perthousand gallons (gpt) per dilution fluid, or between 0.1 and about 100gpt, or between about 0.5 and about 10 gpt, or between about 0.5 andabout 2 gpt.

II. Applications of the Emulsions and/or Microemulsions Relating to theLife Cycle of a Well

The emulsions and microemulsions described herein may be used in variousaspects of the life cycle of an oil and/or gas well, including, but notlimited to, drilling, mud displacement, casing, cementing, perforating,stimulation, enhanced oil recovery/improved oil recovery, etc.).Inclusion of an emulsion or microemulsion into the fluids typicallyemployed in these processes, for example, drilling fluids, muddisplacement fluids, casing fluids, cementing fluids, perforating fluid,stimulation fluids, kill fluids, etc., results in many advantages ascompared to use of the fluid alone.

Various aspects of the well life cycle are described in detail below. Aswill be understood by those of ordinary skill in the art, while certainsteps of the life cycle described below are described in sequentialorder, this is by no means limiting, and the steps may be carried out ina variety of orders. In addition, in some embodiments, each step mayoccur more than once in the life cycle of the well. For example,fracturing may be followed by stimulations, followed by additionalfracturing steps. In some embodiments, refracturing, or the process ofrepeating the above stimulation processes, is further improved by theaddition of an emulsion or microemulsion to the stimulation fluid.

II-A. Drilling

As will be known to those skilled in the art, drilling to form wellborestypically requires the displacement (e.g., using a drill pipe and adrill bit) of reservoir material (e.g., rock, sand, stone, or the like).Such drilling generally requires the use of certain drilling fluidswhich may, for example, lubricate and/or cool the drill bit, assist inthe removal of earth (e.g., cuttings), create and/or balance hydrostatichead pressure (e.g., to prevent, for example, a collapse of the holebeing formed by the drill bit, to control the flow of hydrocarbonsand/or water into the wellbore, to decrease swelling of the surroundingreservoir material), and/or to control or prevent a kick (e.g., anexplosive moving of drilling fluid back to the surface). Non-limitingexamples of drilling fluids include water-based systems, oil-basedsystems (e.g., synthetic oil-based systems, low viscosity oils such asdiesel, crude oil, etc.). In water-based systems, the water may compriseone or more additives, for example, salts (e.g., to form brine), solidparticles, etc. In oil-based systems, the oil can comprise any oilincluding, by not limited to, mineral oil, esters, and alpha-olefins. Insome embodiments, the drilling fluid comprises a foam or a mist. Incertain embodiments, the drilling fluid is a water-based system. In someembodiments, drilling fluids include one or more minerals or additives(e.g., hematite, montmorillionite, barite, bentonite, ilmenite, lignite,lignosulfonate, slacked lime, sodium hydroxide, etc.).

In some embodiments, the drilling fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an additional emulsion or microemulsion in thedrilling fluid may have many advantages as compared to the use of adrilling fluid alone, including, for example, decreasing the swelling ofthe surrounding reservoir, changing (e.g., increasing or decreasing) theviscosity of the drilling fluid, decreasing the amount of water absorbedinto the well during the drilling process, increasing the amount ofwater extracted from the reservoir, changing (e.g., increasing and/ordecreasing) the amount of contaminants and/or particulates extractedfrom the reservoir, and/or increasing the amount of oil and/or gasextracted from the reservoir. In some embodiments, the oil and/or gascomprises an oil and/or gas condensate. As will be known to those ofordinary skill in the art, in some cases, the composition of a drillingfluid may change during the process of drilling.

As will be known to those of ordinary skill in the art, imbibition is anearly instantaneous process that occurs when water comes in contactwith the exposed primary permeability of, for example, water wet shalesand/or clays. This exposed primary permeability may be on the face ofthe drilled cuttings and borehole wall and/or along the faces of thenaturally occurring micro-fractures (secondary permeability). In thecase of secondary permeability, the overall depth of invasion into theformation may be directly related to the depth of the micro-fracturesand the volume of whole water base fluid and/or filtrate allowed toimbibe into the micro-fractures. The speed of invasion of the availablewater base fluid or filtrate into the secondary permeability isgenerally related to the primary permeability features of capillarydiameters and degree of saturation of the shales and/or clays. Theaddition of an emulsion or microemulsion in the drilling fluid may haveadvantages as compared to the use of a drilling fluid alone, including,for example, the controlling imbibition (e.g., prevention, reduction, orincrease of imbibition).

In some embodiments, the drilling fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gallons perthousand gallons (gpt) of drilling fluid, or between about 0.5 and about100 gpt, or between about 0.5 and about 50 gpt, or between about 1 andabout 50 gpt, or between about 1 and about 20 gpt, or between about 2and about 20 gpt, or between about 2 and about 10 gpt, or between about2 and about 5 gpt. In certain embodiments, the emulsion or microemulsionis present in an amount between about 5 and about 10 gpt. In someembodiments, the drilling fluid contains at least about 0.5 gpt, or atleast about 1 gpt, or at least about 2 gpt, or at least about 4 gpt, orat least about 10 gpt, or at least about 20 gpt, or at least about 50gpt, or at least about 100 gpt, or at least about 200 gpt, of anemulsion or a microemulsion. In some embodiments, the drilling fluidcontains less than or equal to about 200 gpt, or less than or equal toabout 100 gpt, or less than or equal to about 50 gpt, or less than orequal to about 20 gpt, or less than or equal to about 10 gpt, or lessthan or equal to about 4 gpt, or less than or equal to about 2 gpt, orless than or equal to about 1 gpt, or less than or equal to about 0.5gpt of an emulsion or microemulsion.

II-B. Mud Displacement

As will be known to those skilled in the art, generally following thedrilling of a wellbore, techniques are utilized to stabilize thewellbore. Stabilizing the wellbore may include inserting a casing (e.g.,metal sleeves, steel tubes, and the like) down the wellbore. In somecases, a cement is injected in the annulus between the wellbore andcasing to add further stability. Prior to injecting cement, additionalfluids (e.g., a mud displacement fluid) may be pushed between the casingand the wellbore sides to remove excess mud and/or filter cake.Generally, a mud displacement fluid refers to a fluid that displacesdrilling mud. A mud displacement fluid is typically injected at highpressure into the inner core of the casing, and exits at the bottom ofthe casing, returning to the surface via the annular region between thecasing and the sides of the wellbore. Alternatively, the muddisplacement fluid may be injected at a high pressure between the casingand the sides of the wellbore and exits at the bottom of the casing,returning to the surface via the inner core of the casing. Anon-limiting example of a mud displacement fluid includes a water-basedsystem. In certain embodiments, the mud displacement fluid compriseswater and one or more solvents, surfactants, and/or other additivesknown to those skilled in the art.

In some embodiments, the mud displacement fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an emulsion or microemulsion in the muddisplacement fluid may have many advantages as compared to the use of amud displacement fluid alone including, for example, preventing orminimizing damage from imbibition, assisting in liquification andremoval of filter cakes, and/or preparing the hole for cementation. Inaddition, the presence of the emulsion or the microemulsion in the muddisplacement fluid may result in improved (e.g., increased) delivery ofthe fluid to portions of the well, which aids in displacing surfacecontamination, which can result in less imbibition, formation blockages,and/or improves surfaces for cementing.

In some embodiments, the mud displacement fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt of muddisplacement fluid, or between about 0.5 and about 100 gpt, or betweenabout 0.5 and about 50 gpt, or between about 1 and about 50 gpt, orbetween about 1 and about 20 gpt, or between about 2 and about 20 gpt,or between about 2 and about 10 gpt, or between about 2 and about 5 gpt,or between about 5 and about 10 gpt. In some embodiments, the emulsionor microemulsion is present in an amount between about 1 and about 4gpt. In some embodiments, the mud displacement fluid contains at leastabout 0.5 gpt, at least about 1 gpt, or at least about 2 gpt, or atleast about 4 gpt, or at least about 10 gpt, or at least about 20 gpt,or at least about 50 gpt, or at least about 100 gpt, or at least about200 gpt of an emulsion or a microemulsion. In some embodiments, the muddisplacement fluid contains less than or equal to about 200 gpt, or lessthan or equal to about 100 gpt, or less than or equal to about 50 gpt,or less than or equal to about 20 gpt, or less than or equal to about 10gpt, or less than or equal to about 4 gpt, or less than or equal toabout 2 gpt, or less than or equal to about 1 gpt, or less than or equalto about 0.5 gpt of an emulsion or microemulsion.

II-C. Cementing

As described herein, and as will be known to those skilled in the art,generally following drilling a wellbore, cement is placed between thecasing and the wellbore sides. At various stages of the cementingprocess (e.g., during preflush, during preliminary cementing, duringremedial cementing, etc.), pieces of cement (e.g., cement particles,ground cement, etc.) may alter the reservoir material or fluid presentin the wellbore (e.g., gelling the mud such that the viscosity issignificantly increased and rendering it generally unworkable), theviscosity of fluids injected into the wellbore, and/or the viscosity offluids recovered from the wellbore. For example, following the cementingprocess, a portion of the cement (e.g., at the bottom of the well, alsoknown as a cement plug) may be removed by drilling, thereby resulting inpieces of cement. The pieces of cement may be removed via injection of afluid (e.g., a cementing fluid) during and/or following the cementingprocess.

In some embodiments, the cementing fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an emulsion or microemulsion in the cementingfluid may have many advantages as compared to the use of a cementingfluid alone including, for example, reducing the viscosity of fluidscontaining cement particles.

In some embodiments, the cementing fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt of cementingfluid, or between about 0.5 and about 50 gpt, or between about 0.5 andabout 100 gpt, or between about 1 and about 50 gpt, or between about 1and about 20 gpt, or between about 2 and about 20 gpt, or between about2 and about 10 gpt, or between about 2 and about 5 gpt, or between about5 and about 10 gpt. In some embodiments, the cementing fluid contains atleast about 0.5 gpt, or at least about 1 gpt, or at least about 2 gpt,or at least about 4 gpt, or at least about 10 gpt, or at least about 20gpt, or at least about 50 gpt, or at least about 100 gpt, or at leastabout 200 gpt, of an emulsion or a microemulsion. In some embodiments,the cementing fluid contains less than or equal to about 200 gpt, orless than or equal to about 100 gpt, or less than or equal to about 50gpt, or less than or equal to about 20 gpt, or less than or equal toabout 10 gpt, or less than or equal to about 4 gpt, or less than orequal to about 2 gpt, or less than or equal to about 1 gpt, or less thanor equal to about 0.5 gpt of an emulsion or microemulsion.

II-D. Perforating

As will be known to those skilled in the art, generally followingdrilling and inserting a casing into a wellbore, perforating guns may belowered into the wellbore to create holes between the interior of thecasing and the surrounding reservoir material. Typically, perforatingguns utilize liquid jets (e.g., hydrocutters) or explosives (e.g., anexpanding plume of gas) to send high velocity jets of fluid (e.g., aperforating fluid) between the gun and the casing to form holes ofcontrolled size and depth into the casing, cement, and/or nearbyreservoir material. During and/or following perforation, the perforatingfluid generally flows into the areas formed by the perforating gun.

In some embodiments, the perforating fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an emulsion or microemulsion in the perforatingfluid may have many advantages as compared to the use of a perforatingfluid alone, including, for example, preventing or minimizing damagefrom imbibition, preventing the formation of new filter cakes (e.g.,that may reduce hydrocarbons in the reservoir material from entering thecasing), and/or increasing the pressure differential between thewellbore and the surrounding reservoir material.

In some embodiments, the perforating fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt ofperforating fluid, or between about 0.5 and about 100 gpt, or betweenabout 0.5 and about 50 gpt, or between about 1 and about 50 gpt, orbetween about 1 and about 20 gpt, or between about 2 and about 20 gpt,or between about 2 and about 10 gpt, or between about 2 and about 5 gpt,or between about 5 and about 10 gpt. In some embodiments, the emulsionor microemulsion is present in an amount between about 1 and about 10gpt. In some embodiments, the perforating fluid contains at least about0.5 gpt, or at least about 1 gpt, or at least about 2 gpt, or at leastabout 4 gpt, or at least about 10 gpt, or at least about 20 gpt, or atleast about 50 gpt, or at least about 100 gpt, or at least about 200 gptof an emulsion or a microemulsion. In some embodiments, the perforatingfluid contains less than or equal to about 200 gpt, or less than orequal to about 100 gpt, or less than or equal to about 50 gpt, or lessthan or equal to about 20 gpt, or less than or equal to about 10 gpt, orless than or equal to about 4 gpt, or less than or equal to about 2 gpt,or less than or equal to about 1 gpt, or less than or equal to about 0.5gpt of an emulsion or microemulsion.

II-E. Stimulation

As will be known to those skilled in the art, generally the completionof the formation of wellbore includes stimulation and/or re-fracturingprocesses. The term stimulation generally refers to the treatment ofgeological formations to improve the recovery of liquid hydrocarbons(e.g., formation crude oil and/or formation gas). The porosity andpermeability of the formation determine its ability to storehydrocarbons, and the facility with which the hydrocarbons can beextracted from the formation. Common stimulation techniques include wellfracturing (e.g., fracturing, hydraulic fracturing) and acidizing (e.g.,fracture acidizing, matrix acidizing) operations.

Non-limiting examples of fracturing operations include hydraulicfracturing, which is commonly used to stimulate low permeabilitygeological formations to improve the recovery of hydrocarbons. Theprocess can involve suspending chemical agents in a stimulation fluid(e.g., fracturing fluid) and injecting the fluid down a wellbore. Thefracturing fluid may be injected at high pressures and/or at high ratesinto a wellbore. However, the assortment of chemicals pumped down thewell can cause damage to the surrounding formation by entering thereservoir material and blocking pores. For example, one or more of thefollowing may occur: wettability reversal, emulsion blockage,aqueous-filtrate blockage, mutual precipitation of soluble salts inwellbore-fluid filtrate and formation water, deposition of paraffins orasphaltenes, condensate banking, bacterial plugging, and/or gasbreakout. In addition, fluids may become trapped in the formation due tocapillary end effects in and around the vicinity of the formationfractures. The addition of an emulsion or microemulsion in thefracturing fluid may have many advantages as compared to the use of afracturing fluid alone, including, for example, maximizing the transferand/or recovery of injected fluids, increasing oil and/or gas recovery,and/or other benefits described herein.

Non-limiting examples of acidizing operations include the use ofwater-based fluids to remove drilling fluids and particles remaining inthe wellbore to permit optimal flow feeding into the wellbore (e.g.,matrix acidizing). Matrix acidizing generally refers to the formation ofwormholes (e.g., pores or channels through which oil, gas, and/or otherfluids can flow) through the use of a fluid (e.g., acidic stimulationfluid) comprising, for example, an acid, wherein the wormholes arecontinuous channels and holes formed in the reservoir of a controlledsize and depth. The addition of an emulsion or microemulsion to thestimulation fluid may have many advantages as compared to the use of astimulation fluid alone, including, for example, the formation of anacidic gel (e.g., which creates a more uniform distribution of acidacross the reservoir materials as it travels along the surface),increasing oil and/or gas recovery, and/or other benefits describedherein.

Fracture acidizing generally refers to the use of an acid to extendfractures formed by the injection of treatment fluid at high-pressure(e.g., fracturing). The addition of an emulsion or microemulsion to thestimulation fluid may have advantages as compared to the use of astimulation fluid alone, including, for example, increasing the removalof fracturing fluid skin (e.g., fluid and solids from the reservoirwhich may block optimal flow of the wellbore) from the fracturesallowing for more effective acid treatment.

As will be known to those skilled in the art, stimulation fluids (e.g.,acidizing fluids, fracturing fluids, etc.) may be injected into thewellbore to assist in the removal of leftover drilling fluids orreservoir materials. Non-limiting examples of stimulation fluids (e.g.,as an acidizing fluid) include water and hydrochloric acid (e.g., 15%HCl in water). In some embodiments, the acid is partially or completelyconsumed after reacting with carbonates in the reservoir. Furthernon-limiting examples of stimulation fluids include conventional fluids(e.g., gelling agents comprising crosslinking agents such as borate,zirconate, and/or titanate), water fracture fluids (e.g., frictionreducers, gelling agents, viscoelastic surfactants), hybrid fluids(e.g., friction reducers, gelling agents, viscoelastic surfactants, andcombinations thereof), energized fluids (e.g., foam generatingenergizers comprising nitrogen or carbon dioxide), acid fracture fluids(e.g., gelled acid base fluids), gas fracture fluids (e.g., propane),and matrix acidizing fluids (e.g., an acid).

In some embodiments, the stimulation fluid comprises a viscosifier(e.g., guar gum) and/or a bridging agent (e.g., calcium carbonate, sizesalt, oil-soluble resins, mica, ground cellulose, nutshells, and otherfibers). In some embodiments, removal of leftover drilling fluids orreservoir fluids refers to the breakdown and removal of a near-wellboreskin (e.g., fluid and solids from the reservoir which may block optimalflow into the wellbore). Non-limiting examples of skin materials includeparaffin, asphaltene, drilling mud components (e.g., barite, clays),non-mobile oil in place, and fines (e.g., which may block pores in thereservoir material). The addition of an emulsion or microemulsion to theacidizing fluid may have many advantages as compared to the use of aacidizing fluid alone, including, for example, increasing the breakdownof the skin into smaller components to be more easily removed by flowfrom the wellbore, increasing oil and/or gas recovery, and/or otherbenefits described herein.

In addition to some of the benefits described above, in someembodiments, incorporation of an emulsion or a microemulsion into astimulation fluid can aid in reducing fluid trapping, for example, byreducing capillary pressure and/or minimizing capillary end effects, ascompared to the use of a stimulation fluid alone. In addition,incorporation of an emulsion or microemulsion into stimulation fluidscan promote increased flow back of aqueous phases following welltreatment, increasing production of liquid and/or gaseous hydrocarbons,and/or increasing the displacement of residual fluids (e.g., drillingfluids, etc.) by formation crude oil and/or formation gas. Othernon-limiting advantages as compared to the use of a stimulation fluidalone, include increasing the amount of water extracted from thereservoir, increasing the amount or oil and/or gas extracted from thereservoir, more uniformly distributing the acid along the surface of thewellbore and/or reservoir, improving the formation of wormholes (e.g.,by slowing down the reaction rate to create deeper and more extensivewormholes during fracture acidizing). In certain embodiments, theaddition of an emulsion or microemulsion increases the amount ofhydrocarbons transferred from the reservoir to fluids injected into thereservoir during hydraulic fracturing.

In some embodiments, the stimulation fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt ofstimulation fluid, or between about 0.5 and about 100 gpt, or betweenabout 0.5 and about 50 gpt, or between about 1 and about 50 gpt, orbetween about 1 and about 20 gpt, or between about 2 and about 20 gpt,or between about 2 and about 10 gpt, or between about 2 and about 5 gpt,or between about 5 and about 10 gpt. In some embodiments, the emulsionor microemulsion is present in an amount between about 2 and about 5gpt. In some embodiments, the stimulation fluid contains at least about0.5 gpt, or at least about 1 gpt, or at least about 2 gpt, or at leastabout 4 gpt, or at least about 10 gpt, or at least about 20 gpt, or atleast about 50 gpt, or at least about 100 gpt, or at least about 200gpt, of an emulsion or a microemulsion. In some embodiments, thestimulation fluid contains less than or equal to about 200 gpt, or lessthan or equal to about 100 gpt, or less than or equal to about 50 gpt,or less than or equal to about 20 gpt, or less than or equal to about 10gpt, or less than or equal to about 4 gpt, or less than or equal toabout 2 gpt, or less than or equal to about 1 gpt, or less than or equalto about 0.5 gpt of an emulsion or microemulsion.

In some embodiments, refracturing, or the process of repeating the abovestimulation processes, is further improved by the addition of anemulsion or microemulsion to the stimulation fluid.

In some embodiments, the emulsion or microemulsion for use with astimulation fluid (e.g., a fracturing fluid) comprising a surfactant asin Formula I:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, R¹² is hydrogen oralkyl, n is 1-100, and each m is independently 1 or 2. In someembodiments, for a compound of Formula (I), R¹² is hydrogen or C₁₋₆alkyl. In some embodiments, for a compound of Formula (I), R¹² is H,methyl, or ethyl. In some embodiments, for a compound of Formula (I),R¹² is H.

In some embodiments, the emulsion or microemulsion for use with astimulation fluid (e.g., a fracturing fluid) comprising a surfactant asin Formula II:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, Y⁻ is an anionicgroup, X⁺ is a cationic group, n is 1-100, and each m is independently 1or 2. In some embodiments, for a compound of Formula (II), X⁺ is a metalcation or N(R¹³)₄, wherein each R¹³ is independently selected from thegroup consisting of hydrogen, optionally substituted alkyl, oroptionally substituted aryl. In some embodiments, X⁺ is NH₄.Non-limiting examples of metal cations are Na⁺, K⁺, Mg⁺², and Ca⁺². Insome embodiments, for a compound of Formula (II), Y⁻ is —O⁻, —SO₂O⁻, or—OSO₂O⁻.

In some embodiments, the emulsion or microemulsion for use with astimulation fluid (e.g., a fracturing fluid) comprising a surfactant asin Formula III:

wherein each of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are the same or different andare selected from the group consisting of hydrogen, optionallysubstituted alkyl, and —CH═CHAr, wherein Ar is an aryl group, providedat least one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹ is —CH═CHAr, Z⁺ is a cationicgroup, n is 1-100, and each m is independently 1 or 2. In someembodiments, for a compound of Formula (III), Z⁺ is N(R¹³)₃, whereineach R¹³ is independent selected from the group consisting of hydrogen,optionally substituted alkyl, or optionally substituted aryl.

In some embodiments, for a compound of Formula (I), (II), or (III), twoof R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr. In some embodiments, for acompound of Formula (I), (II), or (III), one of R⁷, R⁸, R⁹, R¹⁰, and R¹¹is —CH═CHAr and each of the other groups is hydrogen. In someembodiments, for a compound of Formula (I), (II), or (III), two of R⁷,R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr and each of the other groups ishydrogen. In some embodiments, for a compound of Formula (I), (II), or(III), R⁷ and R⁸ are —CH═CHAr and R⁹, R¹⁰, and R¹¹ are each hydrogen. Insome embodiments, for a compound of Formula (I), (II), or (III), threeof R⁷, R⁸, R⁹, R¹⁰, and R¹¹ are —CH═CHAr and each of the other groups ishydrogen. In some embodiments, for a compound of Formula (I), (II), or(III), R⁷, R⁸, and R⁹ are —CH═CHAr and R¹⁰ and R¹¹ are each hydrogen. Inembodiments, for a compound of Formula (I), (II), or (III), Ar isphenyl. In some embodiments, for a compound of Formula (I), (II), or(III), each m is 1. In some embodiments, for a compound of Formula (I),(II), or (III), each m is 2. In some embodiments, for a compound ofFormula (I), (II), or (III), n is 6-100, or 1-50, or 6-50, or 6-25, or1-25, or 5-50, or 5-25, or 5-20.

In some embodiments, an emulsion or microemulsion comprises a surfactantof Formula (I), (II), or (III) in an amount between about 1 wt % andabout 20 wt %, or between about 3 wt % and about 15 wt %, or betweenabout 5 wt % and about 13 wt %, or between about 5 wt % and about 11 wt%, or between about 7 wt % and about 11 wt %, or between about 10 wt %and about 12 wt %, or between about 8 wt % and about 12 wt %, or betweenabout 8 wt % and about 10 wt %, or about 9 wt %. In some embodiments,the emulsion or microemulsion comprises, in addition to the surfactantof Formula (I), (II), or (III), water and a non-aqueous phase (e.g., aterpene), and optionally other additives (e.g., one or more additionalsurfactants, an alcohol, a freezing point depression agent, etc.). Insome embodiments, the emulsion or microemulsion comprises, in additionto the surfactant of Formula (I), (II), or (III), water, a terpene, analcohol, one or more additional surfactants, and optionally otheradditives (e.g., a freezing point depression agent). In someembodiments, the emulsion or microemulsion comprises, in addition to thesurfactant of Formula (I), (II), or (III), between about 20 wt % and 90wt % water, between about 2 wt % and about 70 wt % of one or moreadditional surfactants, between about 1 wt % and about 80 wt % of asolvent (e.g., terpene), and between about 10 wt % and about 40 wt % ofa mutual solvent (e.g., alcohol). In some embodiments, the emulsion ormicroemulsion comprises, in addition to the surfactant of Formula (I),(II), or (III), between about 10 wt % and 80 wt % water, between about 2wt % and about 80 wt % of one or more additional surfactants, betweenabout 1 wt % and about 70 wt % of a solvent (e.g., terpene), and betweenabout 5 wt % and about 40 wt % of a mutual solvent (e.g., alcohol). Insome embodiments, the emulsion or microemulsion comprises, in additionto the surfactant of Formula (I), (II), or (III), between about 20 wt %and 90 wt % water, between about 2 wt % and about 70 wt % of one or moreadditional surfactants, between about 1 wt % and about 78 wt % of asolvent (e.g., terpene), and between about 22 wt % and about 40 wt % ofa mutual solvent (e.g., alcohol). Non-limiting examples of surfactantsof Formula (I), (II), or (III) include styrylphenol ethoxylate, atristyrylphenol ethoxylate, a styrylphenol propoxylate, atristyrylphenol propoxylate, a styrylphenol ethoxylate propoxylate, or atristyrylphenol ethoxylate propoxylate.

II-F. Kill Fluids

As will be known to those skilled in the art, generally during thelifecycle of the well, it may be necessary to temporarily halt therecovery of gas and/or oil (e.g., to repair equipment). Generally, thisis accomplished by injecting a fluid, herein referred to as a killfluid, into the wellbore.

In some embodiments, a kill fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an emulsion or microemulsion in the kill fluidmay have many advantages as compared to the use of a kill fluid aloneincluding, for example, increasing the amount of kill fluid recoveredand/or improving the ability for the well to return to the rate ofproduction it exhibited prior to injection of the kill fluid.

In some embodiments, the kill fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt of killfluid, or between about 0.5 and about 100 gpt, or between about 0.5 andabout 50 gpt, or between about 1 and about 50 gpt, or between about 1and about 20 gpt, or between about 2 and about 20 gpt, or between about2 and about 10 gpt, or between about 2 and about 5 gpt, or between about5 and about 10 gpt. In some embodiments, the emulsion or microemulsionis present in an amount between about 1 and about 10 gpt. In someembodiments, the kill fluid contains at least about 0.5 gpt, or at leastabout 1 gpt, or at least about 2 gpt, or at least about 4 gpt, or atleast about 10 gpt, or at least about 20 gpt, or at least about 50 gpt,or at least about 100 gpt, or at least about 200 gpt, of an emulsion ora microemulsion. In some embodiments, the kill fluid contains less thanor equal to about 200 gpt, or less than or equal to about 100 gpt, orless than or equal to about 50 gpt, or less than or equal to about 20gpt, or less than or equal to about 10 gpt, or less than or equal toabout 4 gpt, or less than or equal to about 2 gpt, or less than or equalto about 1 gpt, or less than or equal to about 0.5 gpt of an emulsion ormicroemulsion.

II-G. Enhanced Oil Recovery and/or Improved Oil Recovery

As will be known to those skilled in the art, generally during the lifecycle of the well, procedures may be performed to increase the amount ofoil and/or gas recovered from the wellbore. Such procedures aregenerally referred to as enhanced oil recovery (EOR) and/or improved oilrecovery (IOR). EOR/IOR typically uses a secondary or a tertiary system(e.g., comprising one or more of water, polymers, surfactants, etc.) tocreate a new mechanism which increases the displacement of oil and/orgas from the reservoir for recovery. Generally, EOR/IOR uses an existingwellbore which has been converted into a recovering well (e.g., aninjecting well). In some embodiments, the recovering well is used toinject the secondary or tertiary system into the reservoir at acontinuous or noncontinuous rate and/or pressure to increase the amountof hydrocarbons extracted from the reservoir. Non-limiting examples ofEOR/IOR procedures include water flooding, gas flooding, polymerflooding, and/or the use of surfactant polymers. For example, theEOR/IOR procedure may comprise an EOR/IOR fluid (e.g., a water floodingfluid, a polymer flooding fluid, a surfactant flooding fluid, a gasflooding fluid, a surfactant, or combinations thereof).

Generally, water flooding (e.g., secondary recovery) refers to theinjection of a water flooding fluid into a reservoir to increase theamount of oil and/or gas recovered from the wellbore. In someembodiments, the water flooding fluid comprises one or more of water(e.g., water, makeup water, etc.), acidizing fluids (e.g., matrixacidizing fluids), surfactants, polymers, and foam. In certainembodiments, the water flooding fluid comprises a polymer (e.g., apolymer flooding fluid), and/or a surfactant (i.e. during a surfactantflood), and/or a surfactant polymer flood (i.e. during a SP-flood),and/or an alkaline surfactant polymer (i.e. during an ASP-flood). Insome embodiments, the water flooding fluid comprises an emulsion ormicroemulsion. Emulsions and microemulsions are described in more detailherein. The addition of an emulsion or microemulsion to the waterflooding fluid may have many advantages as compared to a water floodingfluid alone including increasing the adhesion of the polymer to oil,increasing interfacial efficiency of the polymer, increasing the amountof oil and/or gas extracted from the reservoir, decreasing the volume ofwater needed to extract the same amount of oil, and/or lowering thepressure necessary to extract hydrocarbons from the reservoir. In someembodiments, the addition of an emulsion or microemulsion to the waterflooding fluid increases the recovery of fracturing fluids (e.g.,fracturing fluids not previously removed).

Generally, polymer gels are injected into the formation during secondaryand tertiary recovery to block water and gas (carbon dioxide andnitrogen) flow from previously swept zones and large fractures (e.g.,thief zones) or to prevent imbibition of water from a part of theformation that abuts the oil containing zone. Use of polymers in thesecases is commonly referred to as conformance control or water shut-off.In some embodiments, emulsions and microemulsions are injected into theformation as a preflush to prepare the formation for the polymer gelinjection. The addition of an emulsion or microemulsion prior to theinjection of a polymer gel may have many advantages as compared theinjection of a polymer gel alone including enhancing the adhesion of thepolymer to the formation (e.g., by removing surface contamination andresidual oil).

Generally, gas flooding refers to the injection of a gas (e.g., carbondioxide, nitrogen) into a reservoir to increase the amount of oil and/orgas recovered from the wellbore. In some embodiments, gas floodingcomprises a gas flooding fluid (e.g., liquid carbon dioxide and/orliquid nitrogen). In some embodiments, the gas flooding fluid comprisesan emulsion or microemulsion. The addition of an emulsion or amicroemulsion in the gas flooding fluid may have many advantages ascompared to the use of a gas flooding fluid alone, including reducingthe miscibility pressure as compared to gas flooding alone, and/orreducing the volume of liquid carbon dioxide or liquid nitrogen thatexpands into a gas during the gas flooding process.

Generally, a formulation (e.g., a foam diverter, emulsion diverter, ormatrix diverter) that forms a foam upon contact with gas (e.g., carbondioxide, flu gas, methane, natural gas, or nitrogen) is injected intothe formation (e.g., in an aqueous treatment fluid or injected into thegas stream) that forms a foam upon contact with gas (e.g., carbondioxide or nitrogen) is injected into the formation to divert gas flowfrom high permeability zones to low permeability zones during a gasflood EOR/IOR treatment. These matrix diversion activities are commonlyemployed in situations where gas (e.g. carbon dioxide, flu gas, methane,natural gas, or nitrogen) rapidly penetrates the formation after a waterflooding step without producing additional hydrocarbons. In these casesthe rapid penetration of gas through the reservoir is due to gas gravityoverride or due to exhaustion of hydrocarbon reserves inhigh-permeability zones. In some embodiments, an emulsion and/ormicroemulsion is injected into the formation as a preflush to preparethe formation for the foam diverter injection. The addition of anemulsion or microemulsion prior to the injection of the foam may havemany advantages as compared the injection of the foam alone includingenhancing the stability of the foam (e.g., by removing surfacecontamination and residual oil), or increasing the penetration of thefoam into the formation (e.g., by controlling the adsorption of thediverter onto the rock surface).

In some embodiments, the EOR/IOR fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt of EOR/IORfluid, or between about 0.5 and about 100 gpt, or between about 0.5 andabout 50 gpt, or between about 1 and about 50 gpt, or between about 1and about 20 gpt, or between about 2 and about 20 gpt, or between about2 and about 10 gpt, or between about 2 and about 5 gpt, or between about5 and about 10 gpt. In some embodiments, the emulsion or microemulsionis present in an amount between about 1 and about 10 gpt. In someembodiments, the EOR/IOR fluid contains at least about 0.5 gpt, or atleast about 1 gpt, or at least about 2 gpt, or at least about 4 gpt, orat least about 10 gpt, or at least about 20 gpt, or at least about 50gpt, or at least about 100 gpt, or at least about 200 gpt of an emulsionor a microemulsion. In some embodiments, the EOR/IOR fluid contains lessthan or equal to about 200 gpt, or less than or equal to about 100 gpt,or less than or equal to about 50 gpt, or less than or equal to about 20gpt, or less than or equal to about 10 gpt, or less than or equal toabout 4 gpt, or less than or equal to about 2 gpt, or less than or equalto about 1 gpt, or less than or equal to about 0.5 gpt of an emulsion ormicroemulsion.

II-H. Stored Fluid

As will be known to those skilled in the art, wellbores and/orreservoirs which are no longer used for oil and/or gas recovery maygenerally be used to store excess fluid (e.g., water, makeup water, saltwater, brine, etc.) recovered from the reservoir. In some embodiments,an emulsion or microemulsion is added to the stored fluid. The additionof an emulsion or microemulsion to the stored fluid may reduce corrosionof the wellbore.

In some embodiments, the stored fluid comprises an emulsion ormicroemulsion as described herein wherein the emulsion or microemulsionis present in an amount between about 0.5 and about 200 gpt of storedfluid, or between about 0.5 and about 100 gpt, or between about 0.5 andabout 50 gpt, or between about 1 and about 50 gpt, or between about 1and about 20 gpt, or between about 2 and about 20 gpt, or between about2 and about 10 gpt, or between about 2 and about 5 gpt, or between about5 and about 10 gpt. In some embodiments, the emulsion or microemulsionis present in an amount between about 1 and about 10 gpt. In someembodiments, the stored fluid contains at least about 0.5 gpt, or atleast about 1 gpt, or at least about 2 gpt, or at least about 4 gpt, orat least about 10 gpt, or at least about 20 gpt, or at least about 50gpt, or at least about 100 gpt, or at least about 200 gpt of an emulsionor a microemulsion. In some embodiments, the stored fluid contains lessthan or equal to about 200 gpt, or less than or equal to about 100 gpt,or less than or equal to about 50 gpt, or less than or equal to about 20gpt, or less than or equal to about 10 gpt, or less than or equal toabout 4 gpt, or less than or equal to about 2 gpt, or less than or equalto about 1 gpt, or less than or equal to about 0.5 gpt of an emulsion ormicroemulsion.

II-I. Offshore Applications

It should be understood, that for each step of the life cycle of thewell described herein, the description may apply to onshore or offshorewells. In some embodiments, stimulation fluids are used in onshorewells. In some embodiments, stimulation fluids are used in offshorewells and/or during fracture packing (e.g., gravel packing). As will beknown by those skilled in the art, stimulation fluids for use inoffshore wells may comprise stable media (e.g., gravel) that may beinjected into a wellbore to protect the integrity of the wellboreitself. In some embodiments, stimulation fluids for use in offshorewells are used in high rate water packing wherein stimulation fluids maybe injected at higher rates (e.g., 400 barrels/min), at higherpressures, and/or at higher volumes as compared to an onshore well. Theaddition of an emulsion or microemulsion in the stimulation fluid foruse in offshore wells may have many advantages as compared to the use ofa stimulation fluid alone, including, for example, minimizing thedamaging effects of stimulation fluids that come in contact with thereservoir, and/or increasing the amount of hydrocarbons extracted fromthe reservoir.

In some embodiments, the stimulation fluid utilized in offshore wells orduring fracture packing comprises an emulsion or microemulsion asdescribed herein wherein the emulsion or microemulsion is present in anamount between about 0.5 and about 200 gpt of stimulation fluid for usein offshore wells or during fracture packing, or between about 0.5 andabout 100 gpt, or between about 0.5 and about 50 gpt, or between about 1and about 50 gpt, or between about 1 and about 20 gpt, or between about2 and about 20 gpt, or between about 2 and about 10 gpt, or betweenabout 5 and about 10 gpt. In some embodiments, the emulsion ormicroemulsion is present in an amount between about 2 and about 5 gpt.In some embodiments, the stimulation fluid for use in offshore wells orduring fracture packing contains at least about 0.5 gpt, or at leastabout 1 gpt, or at least about 2 gpt, or at least about 4 gpt, or atleast about 10 gpt, or at least about 20 gpt, or at least about 50 gpt,or at least about 100 gpt, or at least about 200 gpt of an emulsion or amicroemulsion. In some embodiments, the stimulation fluid for use inoffshore wells or during fracture packing contains less than or equal toabout 200 gpt, or less than or equal to about 100 gpt, or less than orequal to about 50 gpt, or less than or equal to about 20 gpt, or lessthan or equal to about 10 gpt, or less than or equal to about 4 gpt, orless than or equal to about 2 gpt, or less than or equal to about 1 gpt,or less than or equal to about 0.5 gpt of an emulsion or microemulsion.

III. Definitions

For convenience, certain terms employed in the specification, examples,and appended claims are listed here.

Definitions of specific functional groups and chemical terms aredescribed in more detail below. For purposes of this invention, thechemical elements are identified in accordance with the Periodic Tableof the Elements, CAS version, Handbook of Chemistry and Physics, 75^(th)Ed., inside cover, and specific functional groups are generally definedas described therein. Additionally, general principles of organicchemistry, as well as specific functional moieties and reactivity, aredescribed in Organic Chemistry, Thomas Sorrell, University ScienceBooks, Sausalito: 1999, the entire contents of which are incorporatedherein by reference.

Certain compounds of the present invention may exist in particulargeometric or stereoisomeric forms. The present invention contemplatesall such compounds, including cis- and trans-isomers, R- andS-enantiomers, diastereomers, (D)-isomers, (L)-isomers, the racemicmixtures thereof, and other mixtures thereof, as falling within thescope of the invention. Additional asymmetric carbon atoms may bepresent in a substituent such as an alkyl group. All such isomers, aswell as mixtures thereof, are intended to be included in this invention.

Isomeric mixtures containing any of a variety of isomer ratios may beutilized in accordance with the present invention. For example, whereonly two isomers are combined, mixtures containing 50:50, 60:40, 70:30,80:20, 90:10, 95:5, 96:4, 97:3, 98:2, 99:1, or 100:0 isomer ratios areall contemplated by the present invention. Those of ordinary skill inthe art will readily appreciate that analogous ratios are contemplatedfor more complex isomer mixtures.

The term “aliphatic,” as used herein, includes both saturated andunsaturated, nonaromatic, straight chain (i.e. unbranched), branched,acyclic, and cyclic (i.e. carbocyclic) hydrocarbons, which areoptionally substituted with one or more functional groups. As will beappreciated by one of ordinary skill in the art, “aliphatic” is intendedherein to include, but is not limited to, alkyl, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, and cycloalkynyl moieties. Thus, as usedherein, the term “alkyl” includes straight, branched and cyclic alkylgroups. An analogous convention applies to other generic terms such as“alkenyl”, “alkynyl”, and the like. Furthermore, as used herein, theterms “alkyl”, “alkenyl”, “alkynyl”, and the like encompass bothsubstituted and unsubstituted groups. In certain embodiments, as usedherein, “aliphatic” is used to indicate those aliphatic groups (cyclic,acyclic, substituted, unsubstituted, branched or unbranched) having 1-20carbon atoms. Aliphatic group substituents include, but are not limitedto, any of the substituents described herein, that result in theformation of a stable moiety (e.g., aliphatic, alkyl, alkenyl, alkynyl,heteroaliphatic, heterocyclic, aryl, heteroaryl, acyl, oxo, imino,thiooxo, cyano, isocyano, amino, azido, nitro, hydroxyl, thiol, halo,aliphaticamino, heteroaliphaticamino, alkylamino, heteroalkylamino,arylamino, heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy,heteroaliphaticoxy, alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy,aliphaticthioxy, heteroaliphaticthioxy, alkylthioxy, heteroalkylthioxy,arylthioxy, heteroarylthioxy, acyloxy, and the like, each of which mayor may not be further substituted).

The term “alkane” is given its ordinary meaning in the art and refers toa saturated hydrocarbon molecule. The term “branched alkane” refers toan alkane that includes one or more branches, while the term “unbranchedalkane” refers to an alkane that is straight-chained. The term “cyclicalkane” refers to an alkane that includes one or more ring structures,and may be optionally branched. The term “acyclic alkane” refers to analkane that does not include any ring structures, and may be optionallybranched.

The term “alkene” is given its ordinary meaning in the art and refers toan unsaturated hydrocarbon molecule that includes one or morecarbon-carbon double bonds. The term “branched alkene” refers to analkene that includes one or more branches, while the term “unbranchedalkene” refers to an alkene that is straight-chained. The term “cyclicalkene” refers to an alkene that includes one or more ring structures,and may be optionally branched. The term “acyclic alkene” refers to analkene that does not include any ring structures, and may be optionallybranched.

The term “aromatic” is given its ordinary meaning in the art and refersto aromatic carbocyclic groups, having a single ring (e.g., phenyl),multiple rings (e.g., biphenyl), or multiple fused rings in which atleast one is aromatic (e.g., 1,2,3,4-tetrahydronaphthyl, naphthyl,anthryl, or phenanthryl). That is, at least one ring may have aconjugated pi electron system, while other, adjoining rings can becycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls.

The term “aryl” is given its ordinary meaning in the art and refers toaromatic carbocyclic groups, optionally substituted, having a singlering (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fusedrings in which at least one is aromatic (e.g.,1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is,at least one ring may have a conjugated pi electron system, while other,adjoining rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, arylsand/or heterocyclyls. The aryl group may be optionally substituted, asdescribed herein. Substituents include, but are not limited to, any ofthe previously mentioned substitutents, i.e., the substituents recitedfor aliphatic moieties, or for other moieties as disclosed herein,resulting in the formation of a stable compound. In some cases, an arylgroup is a stable mono- or polycyclic unsaturated moiety havingpreferably 3-14 carbon atoms, each of which may be substituted orunsubstituted.

The term “amine” is given its ordinary meaning in the art and refers toa primary (—NH₂), secondary (—NHR_(x)), tertiary (—NR_(x)R_(y)), orquaternary (—N+R_(x)R_(y)R_(z)) amine (e.g., where R_(x), R_(y), andR_(z) are independently an aliphatic, alicyclic, alkyl, aryl, or othermoieties, as defined herein).

The term “amide” is given its ordinary meaning in the art and refers toa compound containing a nitrogen atom and a carbonyl group of thestructure R_(x)CONR_(y)R_(z) (e.g., where R_(x), R_(y), and R_(z) areindependently an aliphatic, alicyclic, alkyl, aryl, or other moieties,as defined herein).

These and other aspects of the present invention will be furtherappreciated upon consideration of the following Examples, which areintended to illustrate certain particular embodiments of the inventionbut are not intended to limit its scope, as defined by the claims.

EXAMPLES Example 1

This example describes a non-limiting experiment for determiningdisplacement of residual aqueous treatment fluid by formation crude oil.A 25 cm long, 2.5 cm diameter capped glass chromatography column waspacked with 77 grams of 100 mesh sand or a mixture of 70/140 mesh shaleand 100 mesh sand or a mixture of 70/140 mesh shale and 100 mesh sand.The column was left open on one end and a PTFE insert containing arecessed bottom, 3.2 mm diameter outlet, and nipple was placed into theother end. Prior to placing the insert into the column, a 3 cm diameterfilter paper disc (Whatman, #40) was pressed firmly into the recessedbottom of the insert to prevent leakage of 100 mesh sand. A 2 inch pieceof vinyl tubing was placed onto the nipple of the insert and a clamp wasfixed in place on the tubing prior to packing. The columns weregravity-packed by pouring approximately 25 grams of the dilutedmicroemulsions (e.g., the microemulsions described in Examples 1 or 2,and diluted with 2% KCl, e.g., to about 2 gpt, or about 1 gpt) into thecolumn followed by a slow, continuous addition of sand. After the lastportion of sand had been added and was allowed to settle, the excess ofbrine was removed from the column so that the level of liquid exactlymatched the level of sand. Pore volume in the packed column wascalculated as the difference in mass of fluid prior to column packingand after the column had been packed. Three additional pore volumes ofbrine were passed through the column. After the last pore volume waspassed, the level of brine was adjusted exactly to the level of sandbed. Light condensate oil was then added on the top of sand bed to formthe 5 cm oil column above the bed. Additional oil was placed into aseparatory funnel with a side arm open to an atmosphere. Once the setupwas assembled, the clamp was released from the tubing, and timer wasstarted. Throughout the experiment the level of oil was monitored andkept constant at a 5 cm mark above the bed. Oil was added from theseparatory funnel as necessary, to ensure this constant level of head inthe column. Portions of effluent coming from the column were collectedinto plastic beakers over a measured time intervals. The amount of fluidwas monitored. When both brine and oil were produced from the column,they were separated with a syringe and weighed separately. Theexperiment was conducted for 3 hours at which the steady-stateconditions were typically reached. The cumulative % or aqueous fluiddisplaced from the column over 120 minute time period, and thesteady-state mass flow rate of oil at t=120 min through the column weredetermined.

Example 2

This example describes a non-limiting experiment for determiningdisplacement of residual aqueous treatment fluid by formation gas. A 51cm long, 2.5 cm inner diameter capped glass chromatography column wasfilled with approximately 410±20 g of 20/40 mesh Ottawa sand and thediluted microemulsions. To ensure uniform packing, small amounts ofproppant were interchanged with small volumes of liquid. Periodicallythe mixture in the column was homogenized with the help of an electricalhand massager, in order to remove possible air pockets. Sand and brinewere added to completely fill the column to the level of the upper cap.The exact amounts of fluid and sand placed in the column were determinedin each experiment. The column was oriented vertically and was connectedat the bottom to a nitrogen cylinder via a gas flow controller pre-setat a flow rate of 60 cm3/min. The valve at the bottom was slowly openedand liquid exiting the column at the top was collected into a tarred jarplaced on a balance. Mass of collected fluid was recorded as a functionof time by a computer running a data logging software. The experimentswere conducted until no more brine could be displaced from the column.The total % of fluid recovered was then calculated.

Example 3

This example describes a general preparation method for the productionof diluted microemulsion. The microemulsions were prepared in thelaboratory by mixing the ingredients listed in specific examples. Allingredients are commercially available materials. In some embodiments,the components were mixed together in the orderwater-alcohol-surfactant-citrus terpene solvent, but other order ofaddition may also be employed. The mixtures were then agitated on amagnetic stirrer for 5 10 minutes. The microemulsions were then dilutedto concentrations of 1 or 2 gallons per 1000 gallons with 2% KCl brineand these diluted fluids were used in displacement experiments (e.g., asdescribed in Examples 1 and 2).

Example 4

A number of microemulsions were prepared according to the methoddescribed in Example 3 and comprising the components described in Table2. The microemulsions comprises a styrylphenol ethoxylate surfactant,water, other surfactants, co-solvents, and a solvent (e.g.,hydrocarbon). The percent displacement of brine by crude oil wasdetermined using the method described in Example 1. The results areprovided in Table 2.

TABLE 2 Amount of styrylphenol % ethoxylate used in the displacementExp't formulation Formulation Composition of brine by No. (wt %) (wt %range) crude oil 1 11 ± 1 Water 20-90% 69% Other surfactants 2-70%Cosolvents 10-40% Hydrocarbon 1-80% 2  8 ± 3 Water 10-80% 77% Othersurfactants 2-80% Cosolvents 5-40% Hydrocarbon 1-70% 3 10 ± 2 Water20-90% 83% Other surfactants 2-70% Cosolvents 22-40% Hydrocarbon 1-78%

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e. elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e. the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element or a list of elements. In general, the term “or” as usedherein shall only be interpreted as indicating exclusive alternatives(i.e. “one or the other but not both”) when preceded by terms ofexclusivity, such as “either,” “one of,” “only one of,” or “exactly oneof.” “Consisting essentially of,” when used in the claims, shall haveits ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e. to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. A method of treating an oil and/or gas wellhaving a wellbore, comprising: injecting a solution into the wellbore,wherein the solution comprises: a stimulation fluid utilized in offshorewells, and a microemulsion, wherein the microemulsion comprises a watercontinuous phase, and wherein the microemulsion comprises: between about1 wt % and about 95 wt % water; between about 1 wt % and about 30 wt %solvent, wherein the solvent comprises a terpene and an ester of fattyacid, wherein the ester of fatty acid has the formula R⁷O(C═OR⁸),wherein R⁷ and R⁸ are the same or different and are cyclic or acyclic,branched or unbranched C1-16 alkyl, optionally substituted, wherein theratio of the terpene to the ester of fatty acid by weight is between 1:2and 2:1; between about 0 wt % and about 50 wt % alcohol; between about 1wt % and about 90 wt % surfactant; between about 0 wt % and about 70 wt% freezing point depression agent; and between about 0 wt % and about 70wt % other additives.
 2. The method as in claim 1, wherein the water ispresent in an amount between about 1 wt % and about 90 wt % versus thetotal microemulsion composition.
 3. The method as in claim 1, whereinthe microemulsion is diluted and/or combined with a solution prior toand/or during injection.
 4. The method as in claim 1, wherein themicroemulsion is present in an amount between about 0.1 and about 100gallons per thousand gallons.
 5. The method as in claim 1, wherein thealcohol comprises isopropanol.
 6. The method as in claim 1, wherein thealcohol is present in an amount between about 0.1 wt % and about 50 wt %versus the total microemulsion composition.
 7. The method as in claim 1,wherein the freezing point depression agent is present in an amountbetween about 1 wt % and about 40 wt % versus the total microemulsioncomposition.
 8. The method as in claim 1, wherein the other additivesare selected from the group consisting of an alcohol, a freezing pointdepression agent, an acid, a salt, a proppant, a scale inhibitor, afriction reducer, a biocide, a corrosion inhibitor, a buffer, aviscosifier, a clay swelling inhibitor, an oxygen scavenger, and a claystabilizer.
 9. The method as in claim 1, wherein the other additives arepresent in an amount between about 0 wt % and about 30 wt % versus thetotal microemulsion composition.
 10. The method as in claim 1, whereinthe surfactant comprises a first type of surfactant and a second type ofsurfactant.
 11. The method as in claim 1, wherein the surfactant ispresent in an amount between about 1 wt % and about 60 wt % versus thetotal microemulsion composition.
 12. The method as in claim 1, whereinthe solvent is present in an amount between about 2 wt % and about 90 wt% versus the total microemulsion composition.
 13. The method as in claim1, wherein the fluid is the stimulation fluid utilized in offshore wellsand the microemulsion is present in the solution in an amount betweenabout 2 and about 5 gallons per thousand gallons.
 14. The method as inclaim 1, wherein the microemulsion is injected into the wellbore viastraight tubing or coiled tubing.